i've tried cocomment and co.mments.com and have been less than impressed with both.
It takes forever for cocomment comments to show up (and their support wasn't exactly stellar when i inquired about the problem).
co.mments.com's server is often down or unavailable.
Plus for both of them it involves yet another membership to yet another website, blah, blah, blah.
I just figured that the ability to track my comments was already available via 'My Comments', so a feed for it would be the next logical step. It's not as if adding a feed would add any more clutter to the Dashboard.