Are there a RSS like standard format for distributed (forum like) communication?

To communicate with each other using e-mails users do not need to use the same "provider" (some user might use gmail, other yahoo or hotmail and they still can write e-mails to each other). Unfortunately, it is not like that with social networks. Users using Facebook cannot see posts, comments, likes and shares of the users using Google+ and vice versa.

But why it should be like that? Let us imagine the following architecture. Each user can "broadcast" using any provider he/she likes. RSS format provide this possibility. Any user can choose any "provider" to generate his/her RSS feed and to see RSS feeds of user that he/she is subscribed to. So, just by using RSS as it is we can already build a distributed Twitter-like system (you can post, you can follow other but you cannot share).

What is still missing in this approach is a possibility to comments other posts (liking, disliking or rating could also be considered as comments). In theory one can publish / broadcast comments in the same way as posts. In fact comments are also posts, the only difference is that they are "attached" to other posts. So, one could generate RSS like XML in which some posts (those that are comments) have additional tag that contains URL of the post that is commented.

With such a small extensions of RSS one can build a distributed social network or distributed social news system (like Reddit).

Is there something developed in this direction?