Make shadow profiles of deleted users a seperate distinction
Right now if a deleted user recreates the account, their old notices still have the shadow account URI and this makes the new user unable to be followed because of the software's confusion between the two.
Seperate the two cleanly. Merging is probably not desirable since someone other than the original poster can make the account with the same name if it is deleted.
Probably more of an enhancement than a bug - it doesn't break anything in a major way but it does result in some UX problems.