The list of words deemed inappropriate (which is updated from time to time) is one of those "community standards" issues for which there is no precise method of determination. We try to keep the site family-friendly for ages 13 and up, with admittedly mixed success.
As for asterisks, the rules do not permit bypassing the profanity filter by replacing selected letters with asterisks or similar-looking letters. If "foobar" was on the list, you would not be allowed to say foobar, f00bar, f**bar, foob@r, and so on. The software would catch only the first form automatically, so the moderators would have to clean up posts manually if the other forms were used, assuming the posts were noticed or reported. We would probably permit a one-letter version, e.g., f***** for foobar.
Sorry that I'm off-topic here, but it was a legitimate question deserving an answer.