What is an "illegal characters"?

[Roxbi24]

I'm trying to do a ban appeal, but i can't create the ticker cuz it keeps detecting a "illegal" character. I just read the entire ticket looking for the most minimal offensive word and theres nothing. I'd tried to delete all the special characters like: "-() but its not good enough

I have been trying for about 40 minutes for this ticket, and idk what to delente next. someone knows what a "illegal character" is?

[OhieMitzen]

Try only using letters.