I am of the belief that swear words are there to embellish a point, to bring attention the severity of an issue, or to be seen as casually comfortable with something. Words are powerful things, and kids love to get into anything that is locked away from them.
I know Graal doesn't care about COPPA laws, and I doubt the Graalian forum hosts do either, but there is a legal limit for anyone using these kinds of services; you cannot be under 13 and save profile information such as age, gender, etc. if your web service is anywhere hosted in the United States.
None of that is important, really, but it does give you a good idea of where to start for language: PG-13! So long as we're being American centric, anyhow.