Talking about posting in a simple clear and relevant manner I think your expression on the forum should not be very different from the way you express yourself outside the forum because if you're trying to be different on the forum there is no way that you would not bring in some ambiguity just to make sure you sound sophisticated enough or try to express yourself a little more than you know thus making whatever message you're trying to pass no longer simple and clear even if it still remains relevant. Lack of proper expression distract people from the message whatever post is trying to make and that is why proper expression and clarity is very necessary.