When you go to check your messages on this site, there is an address book function that appears. I've used that to list some of the users whose posts I like to read, or people that I communicate with occasionally by PM. In the address book, if the user listed changes his or her username, it changes in the address book as well. Once or twice I've noticed a name in my address book that I didn't put there and had to figure out who it is based on who I put in there that seemed to have disappeared.
Due to some of what's going on on the site, I've reluctantly started an Ignore List. Do ignored users' names also change in the Ignored Users list when they change their names? If so, this is a great way to keep track of what these nuisances are calling themselves lately. If the Ignored Users list doesn't work that way, I recommend using the address book to keep track of them.
Shiv
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I think we're all Bozos on this bus