Ok, so work out a way to force filtering of certain words/phrases (in a blacklist) even if the filter is disabled and then limit the amount of swear words (would be on a greylist) people can make in a post.
There's probably a plugin for it. If there isn't, it's a trivial job to code a custom plugin for it if you know PHP.
Is filter on? > No > How many swear words in post? > 3 or under > Show swearing
Is filter on? > No > How many swear words in post? > over 3 > Filter swearing after the 3rd greylisted word
Is filter on? > Yes > Don't show swearing









