I've started to look into adding some UTF-8 encoded letters to my text editor(Left), some accented Latin letters, some Greek symbols.. The first thing I did was implement variable code length glyphs, since UTF-8 encoding has characters that span multiple bytes, those would need to be merged into a single sprite. Works pretty nice to add specific characters.
https://git.sr.ht/~rabbits/left/commit/bb184529bc1fbfb73b38112d784e9827a7e37a43
http://wiki.xxiivv.com/site/utf8