

what is the difference in the case of the agent vs. the marble?
The agent made its decision based on knowledge, reasoning, experience, the risks, the morals. A marble doesn’t have knowledge, humans do, even if we’re deterministic, we can make decisions, it’s just that the decision will be made no matter what. That doesn’t free us from the responsibility of our decisions.
Just because the agent would’ve never made a different choice, doesn’t mean these things don’t matter anymore, it’s wholly irrelevant to whether or not we should punish them.
Do you think knowledge, reasoning, experience, and risks do not play any role in our decisions?
Sure, it is inevitable that we will make the decision we make, but it’s not that the marble will fall down every time that makes our choices significant, it’s the fact that we don’t arbitrarily make decisions.
If, because you know about determinism, you stop bothering to learn about the world, there will be a different outcome, even if that was inevitable, that’s how you influence the world. Free will doesn’t mean anything and isn’t important.
Even if there was free will, those things would be vastly more important than it. Free will is totally unimportant.