One suggestion I have made before is actively to upvote comments that either 1) ask for follow-ups with more details or facts to clarify or back-up a parent comment's statements, or 2) provide asked-for details or facts (especially with links to reliable online sources or citations to dead-tree reliable sources). I also like to silently upvote comments in which users are polite and say "please" or "thank you," as a measure to promote civility. What else is good to upvote? How else besides upvoting good comments and asking follow-up questions can each user here promote better comments?
Thank you for any ideas you share here. And many thanks, of course, to the dozens of users here whose posts and comments make HN a valuable community to me and to other users.