Practically speaking, this doesn't seem tremendously useful an idea. Global comment threads are most often a universally repulsive mix of incompatible opinions (case in point: YouTube.) I'll never allow comments on my blog, for instance, because I want to encourage discussions on fora where like-minded (or at least matched intellect) individuals can have a constructive discussion, as happens here on HN.
What would be useful, I think, would be a standard that openly links content to where it is being discussed. I think this would lead to a great surge in discoverability, in terms of both content and communities.
I wouldn't describe HN as an echo chamber. It has elements, of course, but the quality of discourse here is really quite high and respectful. I actually read HN; I don't read YouTube comments, and I wouldn't even if that's all there was.
One of the things that people have against e-mail is it's reliance on base64. Then I see this protocol that just encodes content with base64. It baffles me.
More generally - wrapping the actual content in an encoded envelope was a horrible awful design that was actively hostile to anyone interested in working with the protocol.
What it grants is the ability to sign any content. Which is a pretty important friction point to get past. But I still really don't like it.
I remember something like this around the 2000's or maybe early 90s. I think it was a browser bar. Of course it was centralized, but the idea was there.
