On the site where I am a moderator, if I view the author box for a deleted user, the 'deleted user name' is repeated twice, showing as user12345user12345 instead of just user12345. I suspect this has to do with the difference in viewing as a moderator (moderators get a link) since I am not able to reproduce this on sites where I am not a moderator. I am using Firefox in case this is a browser-specific issue.
/questions?filters=DeactivatedUserson the site (it's a hidden filter for questions from null user IDs that is ordinarily linked only in Teams sites for team admins). (Don't forget to change your filtering type afterwards.)