When I created my new profile a few days ago I was asked to provide my "first name or nickname".  I gave them my real first name which is now my screen name!  I tried changing it.  there's instructions on how to do so buried in the help files.  but it does not work.  So I sent a message to [email protected] asking for their help in changing my screen name.  I'd [prefer a bit of anonymity and would use a nickname.  Here's the reply I just received:

"We regret to inform you that your username or nickname cannot be changed once set, as recent system updates have made it permanent."

I think new users should be made aware of this at the time they are creating their profile!