If you just put an underscore between each word then the redaction moves to units of sentences instead of words. If you permute the underscores with hyphens then each sentence is easily accomplished near factorially with sentence length.
Maybe consider constraining users to real words (like those of the scrabble dictionary) and filter out bad words?
And they made the code for their IRC bot open source, linked to at the bottom of that blog post. The link is now dead, but an archived copy of it can be found at https://archive.ph/d9KMK