I upvote items that are of interest to me, or things I'd rather see at the top of the front page (compared to what is there already). For comments, I'll upvote

I upvote items that are of interest to me, or things I'd rather see at the top of the front page (compared to what is there already). For comments, I'll upvote insight or prosocial behaviour (praise directed at a free software author's comment, say). Plus, anything by people who are clearly authoritative and making posts which contain valuable perspectives. Plus, anything people need to hear. Downvotes I try to reserve for people who are rude, clueless, or obtuse. An example here might be the "but solar panels use fossil fuels for their production" types of comments where the obvious next question - "do they produce more energy than they take to make?" - is left unasked and unanswered by the poster. Disingenuous comments, in other words.