there were a couple of problems that I just couldn't resolve, especially regarding the characters with an iota subscript:
Indeed. This is a problem with the Fontforge code applying the GSUB features: the 'grbl' feature is defined by two lookups, one being a list of single substitutions (h -> eta) and the other a list of ligature substitutions (h bar -> eta with subscribed iota). Now, since the latter has to take precedence to avoid conflicts, I explicitely put it before the other, but it seems that Fontforge ignores this and applies the list of single substitutions before the other (this is confirmed by the cache file BosporosU@greek-babel.tma where the lookup with the single substitutions, called "GreelBabelLookupSimple", appears first in the gsub table). Note that this doesn't happen for substitutions *inside* a lookup (so things like "greater eta bar" and "eta bar" don't conflict since they're both ligature substitutions and I put the former before in the list, and the substitutions are correctly applied. As a far as I understand, this behaviour is actually compliant with the Opentype specifications and is quite widespread among typesetting engines and so it is not (only) Fontforge's fault; but, needless to say, it is nevertheless annoying. (In more crude terms: Opentype does not specify anything in that respect, so manufacturers of typesetting software can do whatever they want ...) Thomas: to solve the problem at hand, you can try the new feature file I send along with a small test (I simply define a new feature that is to be applied after 'grbl', to deal specifically with the subscribed iotas). Arthur