- Summaries of key dynamics/context for the discussion.
- Substantively criticizing other's points.
- References to related materials about the topic in different context and how they're relevant.
How do you worsen the discussion? The opposite of that, plus:
- Misrepresenting arguments or misapplying a citation.
- Replying only to the weakest, easiest version of a point. [1]
- Low-effort in-jokes. ("Hey, maybe they could use a Beowulf cluster for this!" "The mitochondria? Like, the powerhouse of the cell?" Any reference to the IT crowd emergency number.)
Generally speaking, my voting will correlate with whether I agree with a comment. But, two big exceptions:
- If I disagree with the conclusion, but it makes a good case for it that I think merits a response, I'll upvote.
- If I agree with the points, it's done in a trollish way that hinders substantive discussion of the key argument, I downvote. There was one interesting case (I'll try to find it) where the commenter made a great point, and even made a great analogy to one kind of taxation ... but the point didn't need the analogy, and said analogy (predictably) triggered a bunch of commenters to defend their sacred taxation cow at all costs even if they would have otherwise agreed with the main point.
[1] including nitpicking, unless the comment indicates it's doing so, i.e. just fixing a technical inaccuracy unrelated to the core point