I'm not much of a blog comment fan, viewing blog comments as a distant shadow of Usenet, which despite its faults worked amazingly well. So take the following with a grain of salt.
coComment is a comment tracking tool and community which purports to gather all the comments of its users across the blogosphere into one place. For each user, it gives a nice little AJAXy display of all the comments they've made. For a blog, you get a similar presentation of all comments from coComment participants.
I can't figure out whether to file this under solipsism or narcissism.
However, the developers have set themselves up with an interesting Google style problem. I may scoff at the utility, but I have to imagine "organizing the world's comments" is fairly difficult.
You know I've always liked that word... "solipsism" ..., so rarely have an opportunity to use it in a sentence.