Haven't tried this in other versions. If you delete a user who's a Moderator (and probably also an admin), they are deleted fine but aren't removed from the Moderator list (their name still shows up in the forum information screen). Not a huge problem, but if someone discovered this, they can sign-up as that user, and have instant moderator privileges.

Only way around I can find (since you can't edit the Moderator table) is to sign-up as that user, remove them as a moderator, then re-delete them.