I changed my screen name not long ago and I don't like it. Now I can't figure out how to change it back, is that not an option anymore? Before I go requesting permission will someone tell me if the answer is in my face and I'm too tired to notice...
I just checked the moderator board, and found an answer to your question. There used to be a username and a display name - and they could be different and changed on the fly. There was an issue where people could change their display name to be that of someone elses username and so theoretically someone could make it look like they were someone else. Due to that, the admins turned off the ability for users to change their display name on the fly around 5/24.
I looks like a request would have to be made to an administrator to get a name change.