I'm really pleased with the way the commenting system has turned out. Creatively coined as Modnote, it has solved one of the most annoying things I find about other commenting systems out there. The horrible threaded death mess. You know, like the ones you see on livejournal where someone comments on someone else's comments and the width of the column gets narrower and narrower until each comment looks like abstract poetry.
Modnote doesn't do that.
You get to comment on a blog post and people get to respond to your comment. And that's it. The discourse continues from your comment if it is relevant to be responded to. If you want to start another discussion about things unrelated to that particular comment (ie. Offtopicness), you start another thread.
The thing about talking in a crowded room is - people deviate. They go offtopic as soon as they can. Modnote aims to discourage that. Obviously, you can still go offtopic but the commentor after you will still be responding to the original comment. Or at least, it will look like they are due to the layout.
Another thing I like about the design is how commentor names are hidden until you hover over them. So all you see are the comments without the distraction of who and when. You also get a nice, big avatar next to your comment which is nice when you've spent time making it. And if you haven't, you'll want to.
The commentor names are attached to a google search query if wetnote doesn't recognise you. If you've logged in using gmail, twitter or wetgenes, your avatar and commentor name reflects that. Smarts. Otherwise, you get a random Gravatar.
Finally, you get to change the way it looks easily with css. Images/youtube videos/links should be working in them rsn. It's functioning as it should be but at the moment, it's still standalone since management isn't implemented yet. But that's another new thing we're reinventing and i'll talk about it later.
Edit: I should probably give you an example of where this is used so you can see it to its full effect :}
So here it is - http://hoe-house.appspot.com/blog/2344003
Read more about Modnote http://boot-str.appspot.com/about/mod/note