I think this <code></code> and <p></p> parser would be harder to implement than it seems (even keeping in mind your counter points). There are, as far as I have noticed, a fare share of questions that are of the: "I don't understand the difference between grep, map and foreach." written in paragraph form and peppered with keywords and/or small snippets of code. There is also the question of how do you parse out incorrect code/pseudo code.
I do think a short reminder above the poster's displayed previewed text is a decent idea worth exploring. Currently we have: "If something looked unlike you expected it to you might need to check out Writeup Formatting Tips" below the preview displayed post. Maybe that's not clear enough? If, as has been mentioned, the points are terse, few and clearly displayed above the preview, it could be helpful.