An interesting comment system over at Jack Slocum’s blog that uses the Yahoo UI kit with Wordpress. It allows you to comment on any “block” which includes paragraphs, headings, images, etc.
I’ve seen this done in other systems but I do like how it’s handled here. A similar interface was thrown around for commenting on articles in public access journals and possibly a code4lib journal if it ever occurs. Would be a nice addition to some of the Open Journal System layouts. Would also possible be good for repositories.