Write it in google translate then copy paste in the name creation box? Idk. Haven't tried it. Can't try it out right now too coz of emergency maintenance.
You can only use special letters/characters in your name by using the "Rename Card" from the shop (375 coupons). Simply copy paste the special character and it'll work :)
Note: You can't use special characters on the new server account creation screen.
Beware of using special characters in your name. I have a groupmate that we cant contact through PM because his ign has special characters in it. Everytime we send him a message, it says "invalid player".