Yes, keyword density is generally calculated across all the text in the page.
However keyword density isn't really something that is worth worrying about. Agonizing over keyword density is dumb whitehat shit. As long as your page is clearly about $keyword, worry about getting more backlinks. Getting real comments at all is probably a good sign because it means someone is reading your blog.
I do have to say that having commentluv really makes you a target for spammers though.