The commenting system wars are still on, while we might ask if commenting is still relevant. The number of comments have gone down on blogs in the last couple of years, and many different platforms have tried to aggregate comments from other platforms into one stream - with mixed results. That might explain why many bloggers have turned off the commenting altogether. This leads to some dysfunctional conversations on twitter - or to (like I like to do) blog posts that link to the original post (which is no conversation either).
HappyCog have found an interesting solution in my opinion. You can "tweet" your comment directly from the page, or submit a link to your blog post if you prefer to write a longer piece.
Nice idea - I just wonder why they didn't use the same approach for the new "A list apart".