It was intended to be disparaging: one of my major beefs with this community is the massive culture of groupthink and aggressive self reinforcement/adulation.

> It was intended to be disparaging

and thus your thesis of 'HN doesn't like to be reminded' falls to the simpler explanation of 'trashtalk usually gets downvoted'.

Perhaps.

I prefer to see it as the down votes reaffirming that I am correct.

you are correct. if people get triggered by someone using the word "echo chamber" they are probably in one. It's hard to admit, I know.

what do you mean by "get triggered"? if someone downvotes trashtalk, does it necessarily mean they "got triggered"? are there other explanations?

Yes. Because it wasn't trashtalk. HN in generel seems (from what I observe) like a place that uses fancy apps for communication instead of emails. So if someone claims that HN doesn't like emails and get downvoted for that, they got triggered.