Kindness as the default. If it wouldn't fly in a face-to-face conversation, it does not fly on the network. One thing that keeps HN pleasant is dang's enforcement of good conduct.
vs
A crowded network of a mix of educated, spammy keyboard warriors is different.
On HN, we mostly have educated people, so with good conduct rules, they all behave well.
On social networks, you see many keyboard warriors and spammy people, where educated people get overshadowed.