Is swearing acceptable? Damn straight. When used for emphasis or as Spock would call them, “colorful metaphors,” go for it. “Excessive” swearing would be when one uses the words in such overabundance as to dilute their meaning and add no substance. Trying to limit oneself to one or two per paragraph is a good rule of thumb and will allow you to add that extra force you may be looking for without making the whole thing sound deliberately vulgar. Crude sexual terminology and descriptions of sexual acts are also off-limits. We don't care if or how you just got it on with somebody else, nor do we care about your masturbatory habits.
Of prime concern is the use of slurs and words commonly viewed as insulting. Context is important. We recognize that most people don't have any malign intentions, and moderators will do their best to read between the lines and give people the benefit of the doubt when possible. However, slurs that are used exclusively to insult and alienate people because of their race, religion, sexual orientation, disabilities, or any other characteristics are unacceptable and will be treated as abusive behavior. Intent is the most important thing, and intent is without excuse. People who appear to be belligerent or attacking other members will be dealt with accordingly. If you're uncertain whether or not a particular word or saying would be likely to cause offense for any of those reasons, err on the side of caution and feel free to ask a moderator beforehand to be sure if something is acceptable.