Darkners can know swears. Lancer recognizes the word "shit" as one he isn't allowed to say. Rouxls says "God dammit" a lot, which is frequently considered a swear. Characters like Rouxls and Queen also frequently say things along the lines of "thrash your ass". Tenna recognizes "ass" as a swear, and also prevents you from using names that could be used to spell "f**k" or "frick". He also asks that you don't curse if you use the name KRS.