I got a bug when logging in for the first time on appstack and trying to associate my account with my other accounts on the trilogy site. I am using Google Open ID; then I say 'OK' on the Google page to access my credentials; then I am back on the appstack page and I click 'Create Account' and that causes an error ('This is our fault... bla bla').
So I click the login again, Google Open ID again and that logs me in directly. So clearly part of the user creation process worked. However, I did get 'user1021' instead of my normal name shown at the top of my page.
So I came here to post the bug, but I had never registered for this site either, so I go through the same process of account creation and lo-and-behold, I experience the exact same issue! (I get user name 'user147381' this time).
So it looks like a reproductible bug and I even think I know the cause. On StackOverflow, my username is 'AD', 2-letter, that's it. When I try to edit my profile on AppStack, I get an error message when I put in 'AD': 'Display name must be at least 3 characters'.
That's it... I sure hope I can keep my 'AD' name on StackOverflow!
Edit: I can replicate the buggy behavior at will with the 'Copy my profile from StackOverflow' button.