This solves only half of the problem (migration). It doesn't solve the problem of different people signing up on different servers using the same handle. Is there anything stopping me from making a stephenking account on another server?
My "nitpick" was on the use of the word "server". The domain name used for a username is decoupled from the server. But no, there is nothing stopping you from making a stephenking subdomain on another domain. Just like there is nothing stopping you from making a website at google.mycoolwebsite.xyz.
But there are moderation lists that you as a user can subscribe to. It wouldn't be hard to find a moderation list for impersonators, which would solve this problem for you.
