In reply to Chris Aldrich.

Hi Chris, in some ways, the Reader feature of WordPress.com implements some of this. The user can subscribe to websites, read the content, like the content, and respond via comments; all within the Reader.

I think with a bit of tweaking (and desire), Automattic could add the ability to make those comments available as new posts on the commenter's website. It would make WordPress.com (and JetPack supported self-hosted WordPress) more like micro.blog.