in the debate on acid vs alkaline fix for staining/tanning developers, one factor that is ignored is the presence/absence of sulphite/metabisulphite in the fixer. It's interesting to note that PE recommends plain thiosulphate fixer for such developers.
Yes, it's certainly interesting, and sadly we can't ask him anymore. My personal opinion on this is that it's a red herring that may even be down to a matter of definitions. If you just say 'stain', then yes, by all means avoid any sulfite, keep pH high and if you can, run the film through the developer once more after fixing. This will ensure maximum stain.
However! It will not, IMO, ensure maximum
image-wise stain. I.e. the stain that will be formed in a stop bath, fixer and an optional after-bath will be overall/general stain. Essentially, it will be dye-based fog. This is the old myth concerning the PMK afterbath that was dispelled so many years ago; running your film through the PMK again after fixing added to the stain. It sure did, but it didn't add to the image! It just created additional overall density that didn't help in printing whatsoever.
Image-wise stain is formed in a similar way as the dyes in color film or paper: there's a direct relationship between the development of silver, resulting in developer derivatives that form a dye (either by themselves as in pyro developers, or together with dye couplers in color materials). Since no development occurs anymore from the stop bath onward, logically no image-wise stain can be formed from that point. Hence, it wouldn't make sense to maintain the low-sulfite/high-pH environment that's conducive to dye formation.
The only concern you could then have, is that offering sulfite or reducing pH would break down the dyes that have just formed. I'm rather skeptical about this given the permanence of the dyes. Of course, as always, side-by-side testing could be undertaken, and interestingly, apparently this has
still not been done by anyone although it must have been suggested many times over many years now. I admit I haven't gotten round to it yet because I'm working on other stuff right now. Maybe I'll dedicate a few sheets to the matter one of these days.
PS: how come nobody has marketed a staining hydroquinone developer yet? With the interest in somewhat arcane developers, I'd have expected there to be a niche for it. While HQ doesn't stain as heavily as pyrocatechol or pyrogallol, it sure does stain, and it's a fairly pleasant yellow dye at that. Just a tad subtle.