The "preference for generic segregation of the Blechnaceae" is not as clear as indicated above. As Rumsey (2017, Pteridologist 6: 322-323) writes "I think there is clearly the need for more debate before we slavishly adopt all of the proposed changes". He also notes that the PPG has "been criticised for not living up to its ideals for nomenclatural stability".
As indicated by Perrie & Brownsey (2017, N.Z. Bot. Soc. Newsletter 14-17), the PPG made no attempt at consensus at the generic level.
The massive taxonomic change advocated by Gasper et al. (2016) should surely have been strongly justified by its authors. But they offer no explicit reasons for the change.
Arguably, it doesn't stack up very well at all: many of the genera are morphologically variable (as evidenced by the key where many of the bigger genera have to be keyed out in multiple places), so there is little justification there; some of the genera are even more variable morphologically than indicated; there is a interpretive flaw in the conversion of the phylogeny to the taxonomy in that there is no clear evidence that Oceanopteris is monophyletic, so it may need to be combined with Doodia (which would result in a genus not much less variable than Blechnum in the broader sense); and hybridising pairs of species are placed in different genera.

Because the benefits of the segregation do not seem to outweigh the general desire for taxonomic stability, the forthcoming eFloraNZ treatment will use a broadly defined Blechnum.

Perhaps you misunderstand how PPG worked. While there were votes for families and above, there were no votes for genera, unfortunately (which was arguably a significant, even fatal flaw, in the aspiration for a consensus or majority opinion). In the case of the genera in Blechnaceae, the decision was made by a self-appointed committee of 7 that included the 4 authors of Gasper et al. That's obviously not an independent assessment of the merits of the latter.

Consequently, PPG in itself can't be used to provide evidence for "increasing weight and conviction prefers segregation". We've no/little information for what the other 80 or so PPG contributors thought about this particular decision. That will only emerge with time as we see what various people do. Authors connected with the Gasper et al. paper have picked it up for South American treatments. But I think it is too early to tell what the independent consensus is.

The difference in the approaches to Blechnum and Lastreopsis is pretty straightforward, and follows for anyone who favours minimising taxonomic change (while recognising monophyletic groups).
Lumping Blechnum requires about 20-30 name changes globally; splitting Blechnum requires about 170-180 name changes globally.
Lumping Lastreopsis requires about 130 name changes globally (subsuming a paraphyletic Lastreopsis and Megalastrum into the earliest name of Rumohra); splitting Lastreopsis requires 25 name changes.

I'm finding the lump-Blechnum and split-Lastreopsis approaches a fairly easy sell for Botanical Societies etc. Like most taxonomic "end users", they don't like change for the sake-of-change; they want good reasons.
Conversely, I haven't seen a reason that I could use to justify to others why they should split Blechnum and learn a whole lot new names. There is a clear cost, but what is the benefit? The self-aggrandisement of the name-authoring taxonomist doesn't cut it with most "end users". And, resorting to the appeal-to-authority (of PPG) approach doesn't work at least for me, because I see that as an empty argument as I know that consensus simply wasn't attempted at the generic level.

If the rest of the world adopts a segregated Blechnaceae, then I guess we'll have to follow. But that is far from evident yet (and I know of several significant dissenters). In the meantime, I see no merits in being an early-adopter in this instance, given the case for it seems very weak. I'm reminded of the orchid debacle (the flip-flopping with Corybas, Pterostylis etc.), which really put taxonomists in a bad light with "end users". Consequently, I reckon the best approach for now is to stick with the option closest to the status quo.

The explanation tendered to me about how the PPG functioned by Dr Patrick Brownsey (April 2017 - after I read your article in the regional New Zealand Botanical Society Newsletter and queried it) and others who I have spoken to who participated in the PPG process was that you had the opportunity to be appointed to the subcommittees to debate family and genus ranks - but that after those committees were formed their decisions on genera and lower ranks were binding. As Dr Brownsey explained to me last year, you and he elected not to participate in the Blechnaceae subcommittee. So I am not sure of the validity of your statement of the impartiality of 'a self-appointed committee of 7 that included the 4 authors of Gasper et al.'. From what I was told it seems like you could have had an opportunity to contribute to that subcommittee. Irrespective if that really happened then that is indeed a significant flaw in the process and I would agree decisions reached would not necessarily be an 'independent assessment of the merits' of either treatment. However, this was not what I was told was the process so I am not sure how to respond to this allegation - I did not participate in the PPG. However, the same could be argued with the statement regarding New Zealand Blechnaceae 'the forthcoming eFloraNZ treatment will use broadly defined Blechnum' will that be a consensus driven decision or one made by the authors of that treatment (2 people)? Because then you could also argue that the decisions reached may not be objective.

Your comments about Orchidaceae are valid but some more context is warranted. For the Orchidaceae splits its important to note that they were conducted by publication in 'The Orchidian' where the then editor was a good friend of the people proposing the segregation and the peer-review process was not transparent (if it even happened), and in a publication 'The Australian Orchid Foundation' where the contributing authors were also the editors of the same publication they financed and distributed.

In that context that New Zealanders and many Australian's adopted the proposed genera in good faith is indeed upsetting - in New Zealand the segregation was I note largely followed because Landcare Research advised we follow them. It took me four years to get that decision overturned.

In the Blechnaceae situation you have two papers published in peer-reviewed high impact journals that offer alternative ways of dealing with diversity and paraphyly. So the situation is not the same but you are correct that the potential 'fall out' from 'end users' might be. In this regard consider the lumping of Uncinia into Carex - a decision I follow but many in Aotearoa / New Zealand don't like or understand.

Irrespective - this effectively philosophical debate on the merits of 'lumping' vs 'splitting' has little relevance to iNaturalist / Nature Watch New Zealand (though I have enjoyed it). What concerns me is that we have two systems running in tandem in this organization whereby people have already starting loading up the segregate genera (iNaturalist) and like I see for the Hymenophyllaceae there is a disconnect between the genera used simply on the basis of geography - what is Trichomanes in New Zealand is Abrodicytum, Crepidomanes, Polyphlebium etc outside. Close to home I note the same problem exists in the New Zealand Plant Names Database whereby (as of today 26 March 2018) Blechnum vulcanicum, B. fluviatile and B. nigrum are 'preferred' over Cranfillia but the Cook / Samoan Islands Blechnum glabrescens is referred to as Cranfillia glabrescens and that is given in the same database as the preferred name. That being the case it strongly suggests to me a regional problem in the application of genera - you can't have the New Zealand Cranfillia preferentially excluded from it and placed in Blechnum and yet adopt Cranfillia in the same database for those species within it that occur overseas but not in New Zealand. This is rather inconsistent.

Finally - you don't like genera that appear in multiple places in keys. I agree I don't like it either - but its very common, especially in the bryophyte and fungal world (consider Parmostictina and Podostictina vs Pseudocyphellaria). However, that really is a personal preference and if so then I don't like the idea of having to use genera I can't see without doing a DNA sequence - which seems to be the case with Parapolystichum - done it seems to retain a 'lumpers' preference for nomenclatural stability. I am fully aware that the recognition of taxa on the basis of DNA is slowly taking hold - but that so far applies mostly to taxa discovered in eDNA sampling e.g. bacteria, fungi for which no specimen is known (only a sequence) - it remains to be seen how valid that approach will be when dealing with macro-taxa. It certainly was not popular when debated at last years ICN Nomenclature Sessions in Shenzhen, China (July 2017).

Alea jacte est I think.

The title of the PPG reads "A community-derived classification for extant lycophytes and ferns" - that implies to me and others that I questioned and who participated in the PPG meetings and final publication that the classification is intended to reflect a communities decisions not an individuals and as the PPG is dealing with the worlds Pteridophytes and Lycophytes using a global authorship of experts then the connection made by some of its authors and others that it is a 'world opinion' seems pretty fair to me. So I am not going to back down from that interpretation as I am not alone in making it.

The Abstract then reads "Here, we provide a modern, comprehensive classification for lycophytes and ferns, down to the genus level, utilizing a community-based approach". - Again this seems to make pretty clear that this paper is intended to be community based and again looking at the authors on the PPG they span the globe so my usage of 'world opinion' still seems a fair interpretation.

With respect to this debate - encouragingly the abstract then states "This classification is not intended as the final word on lycophyte and fern taxonomy, but rather a summary statement of current hypotheses, derived from the best available data and shaped by those most familiar with the plants in question"

But I'd expect that as a first crack at the problem. So in effect you can ignore it all of course (see below).

The under riding philosophy is interesting and worth quoting in full "We hope that it will serve as a resource for those wanting references to recent literature on lycophyte and fern phylogeny, a framework for guiding future investigations, and a stimulus to further discourse. Although we welcome its use by systematists, other scientists, herbaria, governmental agencies, and others with a professional or non-professional interest in plants, we recognize that a single system may not serve all users and we are strongly opposed to this classification, or any other classification, being imposed on investigators, authors, editors, or reviewers. Disagreements exist even among the contributors to this PPG I classification, as noted below"

No surprises there - but then as an active biosystematist I know I am not required to follow various treatments unless a name has been conserved or a name shown to be superfluous, illegitimate or preoccupied (or whatever) and another put in its place. Ideally I should have the freedom to use whatever names I choose within the strictures of the ICN. But can I? Can I really? Not really - as publication in the world's journals inevitably requires one to adopt a particular classification over another - like the requirement foisted onto a colleague of mine by an editor that he had to use Veronica in preference to Hebe or his paper on pollination biology 'might be rejected'. So despite our code and its decisions classification systems are enforced and unless you have the time and patience to argue around them you end up being made to use ones you don't like or not publish at all.

A digression - mea culpa

So as the PPG repeatedly makes use of 'community' and in its preamble states "we welcome its use by systematists, other scientists, herbaria, governmental agencies, and others with a professional or non-professional interest in plants" - that sure implies that the PPG whose classification I stress was based on a global community of Pteridologists intended it to be used as classification reflecting 'world opinion' in much the same way as the APG is.

Irrespective I can't help but feel that this discussion reads increasingly to me like - I don't like the way a particular classification was adopted so I won't use it.... that's fine when working as an individual - after all I personally disagree with the names being used on iNaturalist for many of the worlds Chenopodium - but even I have to accept that the names used for the genera in the Amaranthaceae on iNaturalist reflect global opinion rather than our regional one. So for example Oxybasis is Chenopodium - at least for now.

Secondly - the key in Gasper et al. (2016). It does not surprise me that some genera key out several times - at least we have characters we can see and use for them. The fact that some genera appear more than once is not unusual or that uncommon in big treatments - consider the keys offered for various liverwort or lichen family treatments of New Zealand / Australasian taxa as close to home examples - or even those that key out 'apparently' one genus - yet include others in them - consider the Lepidoziaceae. The key is merely a tool to help aid determination - its great when each taxon falls out once and only once but pretty hard to achieve as I learned when I did New Zealand Lepidium.