I'm not sure, maybe it has something to do with the account being deleted one way or another? Just a guess but then again, deleted members account names are still there but there is just no link. I'm curious also.
This means that the user has deleted their accounts and is not on SoM anymore or under a different one.
No Spells or post are deleated when somone leaves the site. I have spells and post on here from many years ago.