I rewrite a lot - partly due to a need for perfection, partly due to the dutch-isms I occasionally write. Rewriting a thought is a good thing - it helps to be more precise and concise.
No, I don't rewrite them. To me, a post is like a conversation. You should just type the first thing that would normally come out of your mouth. I figure if people offend easily, they aren't going to like me anyway, so bump 'em.