venting, language, unimportant.
I don't use "heck" very much myself, but I do tend to refrain from certain expletives when communicating online. In person, I tend to pepper my speech a bit too freely, but when I have more time to think--as when I'm typing words out--I don't feel compelled as much to do so. This way it also helps establish that when I _do_ start cursing up a storm in text, it is easier for others to grasp just how aggravated I really am.