When I add a permalink to my profile such as "joshlewis", I cannot clear it from the permalink field the second time I edit my profile. While the validator doesn't have an issue with the permalink field being blank, the value falls back to what it was upon save (I don't think the user can physically see this repopulation issue until checking again).

A user has the right to clear their permalink field if they want to do so due to it not being required data. This also creates minor issues for admins when testing a profile with URL route testing. A real life example would be if my test user has a permalink, in order to test a non permalink profile, I would have to create another test user. There are user scenarios where it may be advised for the permalink to be removed as well.