Another thing altogether, but names like pancäkê can be a problem in that they may limit the ways you may get invited to groups.
Raid group is being formed. Raid leader asks the other group members if they have friends/guildies who could join. One of them has one and he asks the raid leader to invite pancäkê.
Raid leader starts to type:
/invite [character name]
Oh, but the raid leader does not know how to type ä or ê on his keyboard.
So you don't get an invite.
Even if they did find a way around it, that is still extra unnecessary inconvenience for them all.
Don't use umlauts in your name.
Beautiful reasoning, of course. Most people get around this by having the person with the modified characters whisper the leader... however it's an inconvenience in general and really only makes the person using the characters look like a newbie.