A couple issue with that... first of all the whole blank area for who banned looks bad. I can understand how it may not have been a specific person since it was from warnings, but maybe list the moderators that contributed to the ban, or just remove the "banned by" part of the phrase if it's not possible.
Secondly, it says the ban is permanent even though it's not (I have it set to only have someone banned while their warnings are active... in my test, the warning expires 30 days from now).
There are also some usability issues... say you want to see what warnings the banned user has received. They aren't listed in the admin view of the user, nor is there a link to their public profile (which does show them). Even if you manually search for the user to find their profile, you can't find them because banned users are suppressed from the search results.
It would be nice if the username at the top of the "Edit User" page was a link to their public profile (it would also be nice to have a link to their profile in admin area from their public profile if it's a mod/admin viewing it).
Also, why are we hiding banned users from search results if it's a mod/admin doing the searching (someone who has permission to view their profile while banned)?