Upvote and downvote are defined by their operational semantics. There are no formally defined denotational semantics as you're asking for. The operational sema

Upvote and downvote are defined by their operational semantics. There are no formally defined denotational semantics as you're asking for. The operational semantics are simply that comments are sorted by (upvotes - downvotes), and grayed out if that goes negative. (It's slightly more complicated, but that's the dominant factor.) Most people read comments starting at the top, and give up when the comments devolve into crap. So the important thing is to upvote comments worth reading. I upvote things I disagree with if they make an interesting and coherent argument. Perhaps most people would say the same, although people have widely varying inclinations to find things they disagree with interesting.