Comment 15 for bug 7427

This isn't a problem cause of username. If you try to create a user with
fullname "Ante Karamatić", installation will autogenerate username "ante" wich
is OK. But, still, instalation will fail and user will be prompted to create New
user - procedure wich he/she allready did. Username is OK, fullname is a
problem. I didn't do more digging but it seems to me that this isn't a shadow
problem, since shadow doesn't contain fullname at all.

Usernames shouldn't contain accents, and that's normal behaviuor (you don't want
to mess up your keyboard layout and then not be able to login at all to fix
issue), but fullname should be real fullname, with accents.