I should very much desire this feature after hyperblundering today. I edited a post (and was unaware that I was actually posting a new comment instead of being in the edit mode for four of) very many times.

At the least, please change the form button text from the vague 'Submit' to 'Post new comment' and 'Reset' to 'Clear form' when posting a new comment, and the same for when editing a comment: have the button text be 'Submit edit' or something.