, care to exchange link? if so let me know so I can add yours to my blog.
Until recently I was under the impression that the search engines indexed all comments to blogs and sites. However, there's a default setting in a lot of blog template HTML that tells the search engine spiders to "not follow" where the commenter is linking to. (This is to discourage comment spamming as far as I can tell.)
However, there are many bloggers who -- with the aim of encouraging thoughtful comments from other bloggers -- have removed this "no follow" tag so that commenters will get the search engine benefits. These two sites have lists of these "do follow" blogs.