I generally use it for "you're a twat" in general-discussion posts, or "that's actually misleading people" in factual-resource posts. Stuff that doesn't warrant reporting, but I feel should be discouraged nonetheless, by my own personal standards.

Shit takes, unpleasant ideology, aggrieved stupidity, a senseless waste of perfectly good electrons, etc.

It is the crow of jugdement staring back at them.

Disagreeing is fine; I can disagree with people all day and not downvote them over it. Being wrong about stuff doesn't make someone an asshole. However, being an asshole about stuff does frequently make people wrong, which is where the confusion may lie.

I personally think people "should" use the downvote feature on comments that are objectively false, are unrelated to the topic of discussion or on troll/harmful comments

Things that are particularly low effort or that don't really fit in the sub. Blatant marketing outside of AMAs. Rudeness that doesn't break the rules. Double/triple/howevermanyposts. Blatant misinformation that could hurt someone. Anyone that tries to say something nice about spez.

I think that sums up the major categories, off the top of my head.

Upvote high quality, downvote low-quality.

Examples of low-quality:

• off topic

• misinformation

• bad faith

• partisanship

• stereotyping

Low quality does NOT mean "things I disagree with".

For me:

• this opinion is different from mine, but I respect it: ignore
• this opinion is different from mine, and I do not respect it (e.g.: racism): downvote
• this opinion is spreading misinformation: downvote
• this comment is an insult to someone, regardless on whether it was "deserved" or not (e.g.: "this is a stupid question"): downvote
• this comment is breaking community rules: downvotes

I downvote people who post a million comments or replies instead of just using the edit feature. It makes discussion and following a thread super hard for no reason, especially if one reply gets a long chain of direct replies going, and context in the form of a sibling comment to the highest comment of the chain gets lost.

Normally, you should downvote something that does not contribute to the discussion or is unhelpful.

I don't downvote because I disagree with something. I don't think that was the intention.