What’s your “rationalist arguing” origin story?

By rationalist arguing, I mean the sort of argument where you’d rather have the right belief at the end than “win.” This is quite different from the usual rationalization competition style of argument, and is pretty rare. But somehow, it happens on LessWrong a lot. It goes by other names too, but I am contractually obligated to put the word “rationalist” before as many other words as I can.
Back when I was a teenager, and I mean like 13-16, I frequented an online political forum, which shall remain unnamed. It was about as rational as one might expect, which is to say awful. And eventually, after three years visiting there, I stopped. The first mover of me moving out was that I’d figured out the moves on the rhetorical chessboard—if I make an appeal to intuition here, they can make an ad hominem there, and so on and so on. And once this arguing became transparent, it also became boring—instead I started actually asking the question “how can I figure out what’s true?” And so I stopped arguing politics, which had been a pretty big habit of mine a week before.
Cut forward some years. I’m a LessWrong reader. And somewhere after my first few months of posting I figure out that I really shouldn’t be trying to “win arguments” here—after all, I stopped doing that when I was 16, right? Instead, I decide, I should practice “cooperative arguing,” where the goal is to work together (dialectically, though I wouldn’t have known to call it that at the time). And if you’re doing it really right, you should be able to “lose” (in quotes because you’re learning from it and don’t give a crap) about half the time. Don’t “try to lose,” but “try to be able to lose.” There’s a reflection of HPMOR in there, but it’s in a funhouse mirror.
Since then I’ve advanced a bit, so I can look at creating environments that help this happen, but this post was titled “origin story” and that’s what I’m curious about. For me, getting familiar with rhetoric and then getting fed up with it was necessary before I could go on to actually try to be able to lose. But it seems a little specific—there seem (perhaps) to be plenty of other people who follow the same rules as me on here, and you can’t all have frequented political forums during your forumative years (sorry). Or can you?
Was LW key in germinating this “rationalist arguing,” or did we have the seeds already within us? Memory says the latter, but statistics says the former. Or perhaps it’s just a selection effect, and old people who have figured all this out just didn’t tell me. Or they did and I didn’t comprehend.
Gonna need data. What’s your “rationalist arguing” origin story?