So I've successfully changed my username from PewDiePie_Felix to pieoffury in playerdex and I am able to log in with my new username in both playerdex and in game. Can I ask why my name hasn't changed here on forums?
I've already made Bluerise aware of this issue; but if this problem continues for you or anyone else reading this thread, please file a Bug Report on the Playerdex so we can look into it further.