I mean, you can't prove that anyone you meet face-to-face isn't a p-zombie or a projection of your own mind either, but I doubt you're an actual solipsist. And I don't think you honestly have much trouble telling the difference between me and a bot. Yes, for all you know any given person could be a troll or sockpuppet, but you also know with very high confidence that there are many real and sincere people at the other end of the internet.

But maybe we disagree less than it seems:

> I can control my intent, and I have to be satisfied with that.

If this includes modifying what you say when you learn unexpected things about the effect of your words, that makes perfect sense to me.

But if it means refusing to take that information into account, I don't think you can really claim good intentions.