I like hearing lots of opinions about a topic, but do not much like it when a zealot is replying to lots of posts. It subconsciously gives their opinion more weight because I am seeing it many times, though I may not realize that while I'm reading through the discussion.

It would give me more context about a poster to show their comment sequence number for that thread. So for their first post in a topic, something like:

  aardv 16 minutes ago #1 | root | parent | next [–] 

This is a fundamental problem of social media, and one of the ways IMO to have better discussions is to limit people's participation. For example, if a person could only post a handful of times to a topic, they would likely make sure that their comment is important enough to use up one of their limited posts rather than engaging in long back-and-forths with one person. I'm not suggesting any posting limits for HN, but having a count for each user in each topic would at least alert me to maybe adjust my credence filter.