I think cursing comes with a cadence. If you don't have the right cadence, it sounds weird. This is why writing cursing is so hard. When you write what you speak, it looks weird, but when you write something, that looks right; it sounds wrong when you read it out loud.
I heard a script writing for "The Sopranos" on "Fresh Air" and he was talking about how hard it was. He said the best they did was when one guy walked around the room ranting and the other just typed everything he said. It would look weird on the page, but the actor could animate it and make it sound real.