I posted this idea as a joke in another thread, but the more I think about it, the better it feels.
People notice avatars before they notice the username. Avatars can speak louder to your identity than usernames.
I propose modifying the size of the avatar based on the last time it was updated.
Maybe have new avatars at 50% of the current size, getting larger as time passes. Change your avatar, and you go down to the small size.
This way, a person trying to impersonate another user through a similar username and identical avatar would not be successful.
I like it but 50% is bad, the size will be small, IMO. So the % should be decreased.
~~MZ~~