I’m not convinced that is actually happening. I think it’s usually that people deleted when subreddits were private and then things that were not deleted appear when the sub reopens. Sort of dumb that you can’t delete all your content even when a subreddit is private, but there are also wierd things like you can’t see your own comments that were made to people that have blocked you. Dunno if that content reappears after they delete their accounts. Reddit is dumb.