Interesting. I too have seen my articles with the most reads coming from Flipboard and Hacker News. I see a great deal coming from Facebook, as well (and I’m not even on Facebook).
I’ve noticed that two things can get you a huge spike in all 3 metrics (views, reads, recs): getting recommended by the Medium Staff and getting tweeted out by Medium’s Twitter account — both of which happened to me on 3 separate stories. However, those are tough to do.
There are also mirages — things that seem like they’d help you, but they don’t. I have had 2 stories featured in either “Reading Roulette” or in one of the day’s special topics. Neither generated much.
You’re right about publications. Those are key, but tricky. I am a contributor to 8 publications, several of them with tens of thousands of followers. Sometimes they blow up, sometimes, not so much. But in the long term, they definitely help, and the tail tends to be longer as you get more stories published in them.
Regarding publications, though, Medium has some issues with visibility for editors. I’ve had a few stories hang out unpublished and when I pulled them, the editor of the publication claimed they didn’t see them. I’ve also had an issue recently where an editor emailed me to ask for my story, said he requested it through Medium, but I never saw it. It wasn’t until he tried again that it worked.