Dave Winer writes about a technique for tracking conversations on the web: The “You Know Me” Button.
The idea here is that, when you post a comment somewhere, you also authenticate (via the comment server) with an external identity server. From then on, the comment server informs the identity server of any replies to the comment.
As others have said, this is like Passport, except on a smaller scale. Which brings up the possibility of using the identity validation (implied by a successful login to an identity server) to ‘sign’ comments. Current comment systems tend to blindly trust you when you tell them who you are, making impersonation trivially easy. A verified identity could be shown on the comments page.
This might make things a bit tricky, however, as it would need some sort of crypto signature (signed hash of the comment), otherwise server admins would still be able to trivially impersonate others on their own sites. Hmm.
Dave points to SourceID, an implementation of the Libery Alliance protocol. This is interesting, although pretty complex. I don’t think it’s practical to expect all comment server coders / admins to support something like this. We need something simpler - something easy to implement like [[TrackBack]] or [[XML-RPC]].