Yea, users don't have permissions to change their own usernames. If you want to change it, you need to contact a forum moderator, such as Aaron Gertler, JP Addison, Julia Wise and myself (not sure exactly who else has the relevant permissions).
Feel free to add a comment or send me a message with your desired username.
There seems to have been an update since this was posted as I was able to change my username without any additional checks now.
I can't find a way to change my username. I tried a few days before your post and again now. Please advise.
Hi there - it looks like you were affected by our bug, but I think I was able to fix your account so that you can change your username now. If that doesn't work please contact us and we can update your username for you.