Comment Censure plugin allows filtering and censoring comment words. When you use the normal WordPress comment blacklist feature (under Settings -> Discussions -> Comment Blacklist) you enter either a word (or part of a word) and if the comment contains that string of characters then the entire comment gets marked as spam. An easy example is the word “ass”. Sure nobody wants to be called a pain in the ass, or worse, but adding it to your blacklist means that any comment using the words association, passionate, passed or assumption gets flagged as spam. But Comment Censure plugin allows you just filter and replace censored phrases without marking those as spam.
Comment Censure Features