Interestingly, Known had a lot of these features hidden in code under the hood. Sadly they weren’t all built out. It in fact, did have much of a reader (something which Ben indicated they were going to take out of the v1.0 release to slim down the code since it wasn’t being used). It also had a follow/following block of code (and even a bookmarklet at /account/settings/following) so you could follow specific sites and easily add them to your reader. Also unbeknownst to most was a built-in notifications UI which could have been found at /account/notifications.
It’s a shame that they put many of these half-built features on hold in their pivot to focus on the education market and creating a viable cash flow based company as this is the half that most CMSs lack. (If you think about what makes Twitter and Facebook both popular and really simple, I think it is that they’re 95% excellent feed readers with 5% built-in posting interfaces.)
I’ve managed to replace some of that missing functionality with Woodwind, a reader at http://woodwind.xyz, which one could connect with Known to do the reading and then integrate the posting, commenting, and replies to complete the loop. I do have a few very serious developer friends who are endeavoring to make this specific feed reader portion of the equation much easier to implement (and even self-host) to make the hurdle of this problem far lower, but I suspect it’ll be another 3-6 months before a usable product comes out of the process. For those looking to get more social into their feed readers, I often recommend Ryan Barrett’s appspot tools including https://twitter-atom.appspot.com/ which has instructions for extracting content from Twitter via Atom/RSS. It includes links at the bottom of the page for doing similar things with Facebook, Instagram and Google+ as well.
Interestingly there are now enough moving pieces (plugins) in the WordPress community to recreate all of the functionality Known has, one just needs to install them all separately and there are even a few different options for various portions depending on one’s needs. This includes adding reply contexts for social media as well as both the ability to syndicate posts to multiple social sites for interaction as well as getting the comments, etc. backfeed from those social sites back into the comments section of your post the way Known did. Sadly, the feed reader problem still exists, but it may soon be greatly improved.