I've been writing on Google since 1999 (too many content sites to mention). I have also had many of my articles at the top of Google for many years.

Algorithms change constantly for several reasons, i.e. to eradicate black hat seo and to bring the best forward.

In this case, I think Ev is thinking that the writers who interact with their readers are the one's that make readers stay. So the algorithm is increasing for those writers to an extent.

What I've never understood is why the algorithm is intent on making recommendations I clearly don't want to read. And why it doesn't give me the new articles of all the people I want to read. I always keep to Dunbar's number when adding people. That's the most I can acctively read and relate to.