An RSS reader does almost everything I'd expect my fully distributed Twitter instance to do. Only thing missing is ability to post, packaged into the same client.
Somehow this usecase completely eluded me when I've sought about how easy it is to setup a way for publishing updates / receiving updates from people you're subscribed to. I can't think of a way for getting content from random commenters in a discussion with a passive RSS-like subscription. At least not without forcing OP to host links to everyone's comments, or involving a third party.
