My 5 cents on HN's civility is that people want to have an impact with their posts. On large forums (large subreddits, Twitter) you have to be very loud to be

My 5 cents on HN's civility is that people want to have an impact with their posts. On large forums (large subreddits, Twitter) you have to be very loud to be heard. Being outrageous, knee-jerk reactions easily get eyeballs, and don't require much effort or time, hence those who spend effort and time on a post that takes effort and time to understand are outcompeted. Finding content like that becomes a discoverability problem. There is also bandwagoning, adding your vote to the tally doesn't require much effort, but can feel like having an impact by identifying with the collective impact. Apes together strong. On small forums it is relatively easier to have an impact, so because you are guaranteed to be discovered you want to increase the quality of the impact. On a large forum the opportunity to be seen can make you ignore the risk of being judged, and bandwagoning is risk-free, on a small forum the focus is on how you are being seen. On HN specifically most people want to be seen as an insightful, constructive individual. Taking different stances is an established norm here, so the risk is not being upvoted (not discovered, or insightful), or being too downvoted (not constructive). Normally downvotes would also discourage you from taking too different stances, but HN made some smart decisions (you have to have a certain number of upvotes to downvote, can't downvote people replying to you, upvotes and downvotes are not publicly visible, your comment is only greyed out if it has too many downvotes) to encourage different stances and constructive behavior.