I can answer this question! Nominations that come in via the Boost Nomination Pilot account for just less than half of all stories that get selected for Boost. Our internal curation team is organically reviewing stories all day for Boost.

As for a general accounting of Boost categories, I can tell you that based on this week's data, humor is the 12th most Boosted topic, coming out ahead of topics like film, health, and artificial intelligence. Humor is a long way from being snubbed. I wrote a bit about the concerns about topics over here: https://arielist.medium.com/does-mediums-algorithm-punish-spiritual-content-8264bfe3a25f