shadow-banning is handy for spammers and bad-posters because, to them, it looks like their posts are public. Its not hard to find out if you're shadowbanned (use incognito mode), but it often does the trick.

In the subs I mod I have a long list of awful contributors on an auto-remove list executed by automoderator. I've got people who have been saying awful thing to people for years, but those posts are never seen. Banning them will only lead them to create a new account.