Here is an post about bitcointalk account deletation. You can check this. Hope you will be clear.
Deleting accounts doesn't mess up any threads, like
this thread. It just changes to anonymous, with no profile information. Post stays intact.
As you can see here, I only change the username to "Anonymous" on request.
All of the users have anonymous usernames are very old users. I think Theymos no longer accept such requests.
Here is the forum rule regarding changing the username: