There are no official rules against it but there is no real need to swear anyway. If what you're asking is can آپ type words without getting immediately reported, آپ can swear, but it's not necessary is it?
EDIT
Also, if there is some dramatic need یا 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 آپ use derogatory words in an offensives way, آپ can get reported and even banned یا suspended.
Say whatever آپ want, just make sure آپ 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 آپ don't insult your fellow users.