As has been noted in some recent threads, a kind type designer will assign Unicode points to all glyphs so that users can access them in non-Opentype-smart applications.

MUFI defines an unofficial standard for assigning codes in the Private Use Area to a lot of characters and ligatures needed for the precise transcription of Medieval texts. It’s prominently linked from the Wikipedia entry on Unicode, and it includes many ligatures found in modern fonts, like fj and tz.

The fonts I’m working on are never going to be used for Medieval work, but since it otherwise doesn’t matter where in the PUA my extra glyphs go, I feel I may as well put my tt ligature at U+EED9, which at least someone has already agreed corresponds to a tt ligature. I think it’s even reasonable to find approximations; for instance, my swash P alternate can go in the place meant for “capital P with flourish”. It’s not really the same thing, but it’s a P, and that’s better than random. MUFI spans E000-F2FF, so glyphs without an applicable MUFI encoding should start at F300, because if half the special characters turn into the right thing when a text is changed to a MUFI font, the other half should become .notdef, not the wrong thing.

What are your opinions on using these codepages this way? Do you think it’s a good idea, or a bad idea?