Hi @downey, would you know how to change our username if we don't see the 
button? Similar to you, I am trying to change mine from Marc_Abbyad to just abbyad.
On How to create your account and claim your old emails/posts I see this note:
If you are not happy with the default username, change it now in Preferences. You will not be able to change it later!
I hadn't noticed the edit option then, and hope I haven't missed my chance! 