"Is the like/dislike button meant to express a values-neutral judgement of quality, or is it meant to just track who agrees or disagrees?"

This. I don't even know WTF the "like" button is supposed to represent here. I just do it as a lazy "good post!" It doesn't mean I endorse every single idea contained in it; and behind that is a far more sinister concept; that "likes/dislikes" or "upvotes/downvotes" determine what is acceptable speech on the internet

this is why social media sucks