I have changed my mind on things in online discussions. Usually in the form of them saying something I disagree with, me trying to articulate why they're wrong or searching for evidence that they're wrong, and then coming up short or finding information I wasn't previously aware of. I find this is more likely to happen online than IRL since you don't really interrupt IRL conversations to go spend 3 hours looking for sources, though I do also get what you mean about a lot of online comments being so blatantly hostile that you just don't engage.