It's a series of gates too, right? To propagate (show up on more feeds), they need people to interact with it. So successful content will be that that best dri

It's a series of gates too, right? To propagate (show up on more feeds), they need people to interact with it. So successful content will be that that best drives interaction, and I guess comments still weigh more heavily than likes? Consequently, Facebook itself is a brute force algorithm for discovering the more virulently memetic content and phrasing.