Andrew Orlowski is right, there are too many blank "Discussion on..." pages in Google results, but only if you're using search words like 'discussion', 'trackback' or 'comments'. On the flip-side, I've been noticing the advantages of embedding comments and trackbacks in single-post archive pages - commenters leave lots of extra keywords that you might have missed, and Google indexes all these along with your original post. Bonus added value, or something.