I tend to upvote a post when it Links an interesting article or provokes an interesting conversation, and only downvote them when they voice an convectively bad opinion (like, bigotry or other unjustified vitriol).
I tend to upvote comments when they make a good point or at least try to support their argument, and only downvote them for the same reason as posts: when they are trolling, being unnecessarily aggressive, or trying to justify bigotry with fallacious reasoning or something
What about you?
If there’s a community I want to support I generally go in and upvote every comment on every post. Unless it’s mean, then it gets a downvote or a removal if it’s bad enough and breaks the rules and it’s in a community I mod and have god-like powers in.
I try to upvote anyone that responds to me, even if they disagree with me, or I with them. It feels petty not to.