jits, why did you vote -1 on it?
Some people like to hop on a server just to play and be left alone, so they use an alternative (but registered) name. If it becomes really easy to check what their other names are, then they may start playing without being logged in, register multiple accounts, etc. I would prefer that people just use the login system the way it was meant to be used, so I rather not to implement features that might discourage that.