Interesting questions. Honestly, while Medium claims this approach will remove the possibility to game the system, because it's supposedly more transparent, I think it actually achieves the opposite. I for one like a system where something goes viral organically. No boost options of any kind. There are plenty of indicators that a system can look at and decide if the content is worth pushing to more users or not. Take for instance a LEGO article. Push it to all users who either are fans of the topic or interacted with LEGO related articles before. YouTube does this really well. I can literally change my feed in a week, by watching different content than I used to. The "involving the human" transparency claim that Medium makes here is incredibly brittle, because now you're already feeling like wanting to contest a boosted article. Suddenly it becomes a fight between authors, publications and Medium. To what end?

Just today, I left two publications, one of them Codex. Because after careful consideration, I think it's sub-par, and I say that as an ex editor of Codex. Illumination is probably next on my list to abandon. You are right that some of the mechanisms for Boost seem to have always been there, it's just a remix of them. Regardless, I think my bottom line is that we don't need any kind of community curation. Let writers do their best to shine and let readers be the ones who decide what goes viral. This would actually save Medium money, as it would have a lot less infrastructure to maintain.

I don't think editors will be asked to recommend from articles outside the publication. You'd have to have a massive system for that to be enforced. Some might do it voluntarily, but that's a small number, quite insignificant to the point that you might (if you're lucky) get one Boost a year.