the ones that are not focused on professional, commercial or business opportunities, like LinkedIn is, at least remove one of the motivations to lie. Those that offer full anonymity, remove another.
We weren't discussing truth, but honesty. Someone deluded can still be honest given what they (falsely) believe.
Besides, I wrote about how there are multiple incentives to lie, and a platform were you're not having a financial interest in what you write, removes some big ones. Doesn't mean something like 4chan doesn't have others.
Still, I'd expect to find a homest to god personal confession in 4chan or Reddit way more than on LinkedIn.