Best commenting systems

One thing I've noticed has been the micro-innovation within the blog commenting space. Some developers are getting pretty clever with displaying the feedback their posts generate. This makes reading the comments almost as much fun as the main article itself.

The two best examples I've found are those on Softies on Rails, Digg, and the Django Book beta site. Many of them leverage script.aculo.us to do DHTML wipedown animations and such. Very impressive.

What cool, outside the box commenting systems have you noticed?