There are no official rules against it but there is no real need to swear anyway. If what you're asking is can anda type words without getting immediately reported, anda can swear, but it's not necessary is it?
EDIT
Also, if there is some dramatic need atau older people in a story, it makes sense that swearing would be included then.
Yes, it is technically not against rules and/or guidelines to swear, but if anda use derogatory words in an offensives way, anda can get reported and even banned atau suspended.
Say whatever anda want, just make sure anda have a valid reason. :/
Well, I do occasionally drop the F-bomb and such, but only when it's really necessary to express my feelings. It's not prohibited since anda don't insult your fellow users.