Name changing suggestions

the issue type is not a bug its just that it wouldnt let me choose any others, this is a suggestion, have "fingerprints"
EXAMPLE
if my user name was "jeb_" then when my account was created i was assigned an alpha-numeric code (such as "587sj3i8rju3ijdu3ureidu)that was unseen then when i change my user name to say "Clistenese" my finger print (587sj3i8rju3ijdu3ureidu) stays the same, and then servers use the finger print to ban players by typing a command such as /Clistenese finger