I think HN is generally inhabited by intelligent but highly opinionated people. Sometimes an opinionated discussion can degenerate into a frivolous argument even between well-meaning parties. It's helpful to have input from someone whose aim is the furtherance of productive discussion. Often all it takes to turn a flamewar back into a reasonable debate is a prod in the right direction. Generally the argumentative parties (myself included, perhaps included foremost) were only carried away; many good conversations can be salvaged with a bit of third-party influence. Obviously this doesn't apply to trolling, etc., and I don't think heavy-handed modding is a solution, but at least in the threads I've seen you participate as a mediator, it has been beneficial.