According to Jeff Atwood, expletives/swearing is not acceptable behaviour, and can result in suspension.
I'm fine with this, and completely condone this. One can still convey a rational point without these words.
However, there are...varying levels of expletives. Some are stronger than others. Do we ban all of these, even simple almost innocuous 'replacement' ones like "heck"? What about "dang"? Certain f-bombs or c-bombs I can understand, I'm just curious, as it's come up on travel>SE a couple of times (fortunately I no longer have to moderate that though!) :)
EDIT - just noticed it's in the [help] as well:
Please note that expletives are not allowed. If you use expletives on this site, you may be issued a warning or a suspension.
but again, there's no indication of which words.