I'd like to hear you expound on that.
I tend to think of it being more about the mode of communication (it being text-based, and not with people you interact with outside the virtual forum), rather than how it is structured, but I'm interested in hearing other thoughts as well.
I think you are correct in what you are saying- the text based format (which can lead to a lack of nuance and inability to discern tone) is part of it, the perceived anonymity (or virtual distancing even on platforms that have real names) is part of it.
But... I also think that the very structure leads to argument as well. Most of us have heard some variation of
Cunningham's Law- "The best way to get the right answer on the Internet is not to ask a question; it's to post the wrong answer."
However, most people don't realize that this was coined in the '80s.... and was about Usenet.
I think that there are a confluence of factors- the most obvious is that people are less likely to engage to say, "You're right!" Sure, some do ... but seeing something wrong ... on the internet ... that really motivates people to actually write something. I think that this is a common experience; you see a person post something that you agree with, and you might (if it is offered) give a "like," but you are probably less motivated to say, "Snarf. I noticed that, as always, you are correct. BRAVO!"
On the other hand, when you see something wrong, you just can't help yourself.
I think it's also a function of threading and replies; you reply, you are quoting someone. Usually, that "pings" them, and if you are disagreeing (in whole or in part) with something they wrote, that tends to make them reply to you, and then you are pinged, and you reply, and then ...
I am sure there is something something science about endorphins and notifications, but that would require me to do research.
Finally, I think that classically, there's the idea that you have
thesis :: antithesis :: synthesis. But people on the internet are rarely interested in discussing things in that fashion; the nature of a forum is conducive to staking a position and holding it, so you rarely get to the synthesis. It's more
thesis :: antithesis :: strawman :: logical fallacy :: yo mama.
But overall, I think that there is something structural that tends to promote argument over discussion; it's not that you can't have places with good or great discussion, but that structural forces act against that to the extent that we need to act against it.