It is a first time I am using a mailing list. I hope I do this correctly. :)
I am quite new to FontForge (or font designing software in general), so perhaps this problem is trivial. The thing is: after adding some GSUB lookups to my font, all of my painstakingly designed kerning stops working. While testing the generated otf file the substitutions work as intended, but the positioning is gone. When I go back to FontForge, remove any GSUB lookups and generate a new file, kerning works fine.
I find this quite baffling. I thought it normal for most fonts to use both kerning AND ligatures. ;)