> All of them? If not, how to determine which ones?

How does it determine how to respond to any prompt? Exactly. It might reasonably predict responses to those comments that, according to its black box, are somehow most likely to receive a reply. Different GPT instances prompted or trained to have different personalities would choose differently based on their priors and biases.

I'm pretty sure the vast majority of human beings are able to reason without really having the slightest idea as to how exactly they do it. Educated humans can use language to talk about reasoning in terms of logic, and even make logic engines out of doped silicon and whatnot, but as of now, none of us has any idea of how reasoning is implemented in the mass of fat and protein that's inside our heads.