For this to work, the upvote would likewise have to cease meaning "agree" and instead mean "good answer." Unfortunately that'd be a step too far for most people. At the end of the day, entertainment, not edification, is the primary driver for most people to be on social media. So they need a way to express favor for answers that are enjoyed even if they don't lead to deeper discussion.
Perhaps a three button system would work.
All that said, I also would love there to be less lazy comments.