Perhaps that would be an easier solution than notifications or marking deleted posts, a read only subforum where all user deleted posts are moved, available for all to read.
We need to somehow see deleted posts because.......
preferably in the self moderated topic, in bold print. that way, if someone reads the topic, sees there are 50 deleted posts, and the remaining 12 posts are all positive, they can notice.
wouldn't that make it way too easy to get 'legit' threads to look suspicious? just post 50 off-topic replies, wait for OP to delete them.