On numerous occasions, I have posted an unfinished comment by accidentally pressing the return key on my iPad. (I personally think you should have to press the “Add Comment” button on the site to submit the comment, so that this can’t happen.)
I deleted each comment as soon as I accidentally posted them. Could the system detect this as abuse, and I get penalized for it? I don't try to do it, but sometimes I accidentally press the return button instead of another key.