As an Online Person for nearly 40 years, many things in this resonated with me. The "engagement has a sample bias" part seems particularly relevant, and neither OP nor I are the first to notice that people are more likely to speak up in disagreement than in support.
Overall, I think many of the ills that OP describes come back to the same thing: writing on the internet is mostly more like public speaking than normal conversation. This is especially true for blogs, but even in places like Twitter or here there's a division between you as writer and many strangers as readers. That's not how people normally operate IRL. In-person discussions are usually among only a few people, up to maybe a few dozen in a big conference room, and they're more interactive. One-way speaking in front of hundreds or thousand of strangers is something many people never do, and many more consider it the most anxiety-creating thing they've done. But here online, we all do it all the time, and we all learn to do it in a very particular way - using the voice of authority (or the "high school debate club" voice) instead of our normal conversational voice, anticipating disagreement or even hostility (see above about sample bias), and so on. The more antagonistic the forums you've been in, the more you'll adopt that style yourself. Just look around right here. It wouldn't be at all surprising to see examples outing themselves in replies to this very comment. And yes, I'm exemplifying that tendency myself. It's deliberate, so no need to call me a hypocrite for it.
I've been thinking about ways to foster a more "living-room-like" environment without these malign effects, but haven't really come up with anything. Maybe the so-called metaverse - for all the other issues with that concepts - will at least feel real enough that people will feel inclined to interact as their normal selves instead of as their current (and generally not so congenial) internet selves.
Overall, I think many of the ills that OP describes come back to the same thing: writing on the internet is mostly more like public speaking than normal conversation. This is especially true for blogs, but even in places like Twitter or here there's a division between you as writer and many strangers as readers. That's not how people normally operate IRL. In-person discussions are usually among only a few people, up to maybe a few dozen in a big conference room, and they're more interactive. One-way speaking in front of hundreds or thousand of strangers is something many people never do, and many more consider it the most anxiety-creating thing they've done. But here online, we all do it all the time, and we all learn to do it in a very particular way - using the voice of authority (or the "high school debate club" voice) instead of our normal conversational voice, anticipating disagreement or even hostility (see above about sample bias), and so on. The more antagonistic the forums you've been in, the more you'll adopt that style yourself. Just look around right here. It wouldn't be at all surprising to see examples outing themselves in replies to this very comment. And yes, I'm exemplifying that tendency myself. It's deliberate, so no need to call me a hypocrite for it.
I've been thinking about ways to foster a more "living-room-like" environment without these malign effects, but haven't really come up with anything. Maybe the so-called metaverse - for all the other issues with that concepts - will at least feel real enough that people will feel inclined to interact as their normal selves instead of as their current (and generally not so congenial) internet selves.