Finally got around to updating the avatar archive to be able to find text files with additional information about the avatars and display these as tooltips if they exist (as well as upgrading from simple image mouseover titles to CSS tooltips as a prerequisite for this).
I don't remember seeing this happen before, but the Search, Notifications, and Checkout buttons now seem to have both the CSS tooltip and a regular image tag title. The latter seems a bit unnecessary and likes to show up on top of the former.