>I think by playing the brinksmanship card of "there can be no level-headed discussion" you inadvertently discount a lot of perfectly coherent and important digression, on both sides."
The brinksmanship card of HN is the reverse of this framing: There must be level-headed discussion. To wit:
>The most important principle on HN, though, is to make thoughtful comments. Thoughtful in both senses: civil and substantial.