I "jot":http://ichris.ws/2006/02/05/30-boxes-cocomment about "coComment":http://www.cocomment.com/ in early February and had been using it on and off. Aside from the annoying fact that you need to change your commenting habit to make it work (click a bookmarklet before hitting submit), its biggest flaw was not being able to track comments made by non-user of their service. They also require blog engines to modify their code & template to work with their service.

The application idea was great, but that last 2 facts ruined any chance of it really becoming useful. The creator had of course had more than earfull of this feedback, and said to be "working on it":http://www.cocomment.com/teamblog/?p=49 since early March.

Then "co.mments":http://co.mments.com arrived on the scene. It doesn't require blog engines tweaks, tracks all comments, and even work without you needing an account.

I don't know if co.mments _borrowed_ the idea as well as the service name idea, but it's not something someone whipped up on a free weekend. The post crawler is intelligent enough to understand most engines I tried it on. And the "no-account mode":http://wiki.co.mments.com/Registration works well.

Right now, my 2 peeves about co.mments are

* It sometimes get the post title & content wrong. When this happens, it either use the first sentence of a post content as title, or display no titles whatsoever. Having said that, being able to do this much without any change on author's side is an amazing feat already.
* I have to scroll a lot on the _Track_ page to find new comments. A collapsible interface ala coComment will be very welcomed. (Assaf "said":http://blog.co.mments.com/2006/03/18/site-redesign/ he's working on it.)

P.S. A few days after I started using co.mments, coComment's host was down for a long period with DDoS attack. Not a good week for the coComment folks.