I don't see how a system like this would improve comment quality. In my opinion, high comment quality is strongly related to the atmosphere of respect on HN.

I don't see how a system like this would improve comment quality. In my opinion, high comment quality is strongly related to the atmosphere of respect on HN. Making comment scores private helped with this. Creating complex rules, or rules that mysteriously favor the votes of some users relative to others, leads to the perception that HN is a caste system, even if status is earned over time... and nudges the atmosphere more toward competition than friendly discussion. The one feature that I think could be useful would be some way to merge stories that are essentially identical. There is a karma incentive for people to post lots of stories about topics that are "trending" at the moment. The more users we have, the more thorough the community will be with this, and it's both a good thing and a bad thing. The upside is deeper coverage of important events, the biggest downside is a fragmented discussion, but in addition the homepage is often filled with 4 or 5 (or more) highly similar stories. Adding "merge" would improve the s/n ratio, reduce redundancy in the discussions, and make it easier for someone checking HN at the end of the day to get up to speed on what happened and to (perhaps) leave an insightful comment or two.