I don't downvote unless it's an obvious troll. I upvote if it's well written ANDOR it's a well-made point. If I get into a debate in the comments with a smart person, I upvote every reply they make to remind myself that they deserve respect.
On other platforms, I have come to believe that it is healthier for me to reply to content that I feel good about upvoting, and just moving on if I am tempted to downvote.