Ah good question and sorry that wasn't clear—I use that word a lot. By "activation" I mean arousal of the nervous system, particularly the sympathetic nervous system, which regulates fight-or-flight responses, and the limbic system of the brain which assesses threats and seizes control when it feels that survival is threatened.
What happens in flamewars is that when people encounter material they strongly disagree with, these systems get activated and rapidly produce aggressive and defensive responses that have to do with self-protection, and nothing to do with thoughtful consideration of the material, things one might learn, points where one might be wrong, curiosity, playful interaction, and so on. When survival is at stake there is no time or space for the latter sorts of reactions. But it's the latter that we want on HN—they're what the site is for.
Of course we all know cognitively that our survival is not really at stake when someone disagrees with us on the internet—at least our frontal cortices know that—but our limbic systems and autonomic nervous systems definitely do not know that. They experience it as a threat and from then on it's kill-or-be-killed. The fact that survival is not really at stake has no effect; what matters is the feeling that it is so.
This is what underlies commenters being so angry, snarky, sarcastic, aggressive and so on, on the internet. It's also what underlies our inability to hear each other or respect each other.
I sometimes describe this is as 'reflexive' vs. 'reflective' responses (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...). By 'reflexive' I mean when the rapid-response system I just described takes over and reacts from "cache", so to speak, to quickly counter
a threat. By 'reflective' I mean the slower processes that happen when one is in a relaxed state and available for curiosity and play. In the jargon I'm using, 'activated' means being in 'reflexive' mode, and 'interested' or 'curious' means being in 'reflective' mode.
This has all kinds of interesting aspects. Here's one: you can't be in both of these states at the same time. It's literally one or the other. Think of the implications that has for a community like HN, where basically everything we want comes out of one of those two states and everything we don't want comes out of the other.
Someone is going to object that political developments can and do present real survival threats. That of course is true, and maybe to the extent that it is true, people have no choice but to function in kill-or-be-killed mode. But we feel this way and behave this way to a greater extent than we need to, and that's one factor preventing conflicts from being solved. That's a vicious circle which it's in all our interests to explore our way out of. We can't kill our way out of it.
In case it's not obvious, I'm using the word 'kill' metaphorically. What I mean by 'kill' is what we do when we try to eliminate threats (and the feeling of threat) by annihilating the other. That shows up as real killing in extreme situations like war, but the same (let's call it) psycho-physiological state shows up in other environments too, including trivial ones like internet forums. Here it shows up as people trying to annihilate the other by maximizing the aggressive potency of their language.
How do we end up getting so activated when we don't need to? and what can we do to become less activated in this way? I believe that if you tug on those threads and keep tugging, you arrive at the most important problem in the world. That's one main reason why I've kept working on HN for so long. Internet comments are trivial, but this environment is a laboratory for learning about this stuff—not just by observing others, but mainly by working with what they activate in oneself. In that sense it's a driver for growth and learning. This learning isn't primarily conceptual—it's more somatic.
p.s. Lots of people on HN know far more about the physiology here than I do. What I'm saying comes from my explorations of the therapy world, e.g. somatically-oriented trauma therapies and even-more-out-there stuff. That culture veers into metaphor more often than genuine specialists would be comfortable with. If I've done that in this comment I would certainly be interested in correction!