In several cases, users wants to delete their own user account.

It goes against law not to allow them to do that (for instance in France, if someone does not want you to have data regarding him, you have no option).

So this feature should be added. Indeed, it implies that first the user should have to confirm by mail his choice; and then, the process should first put the user out of this projects. Finally, the account should probably kept to avoid item history breakage. That would mean erasing everything of the account, just keeping the username, and replacing the realname by "$username - account deleted". In that way, there would be no longer anyone able to log in, or whatever, but we would not have to create specific flags.