The statement 'The payouts are the same regardless of what you do' is in the context of a person's state of mind; someone can either 'behave as if there is or behave as if there isn't' free will.
We are for our purposes only concerned about the situation where there is no free will.
The main issue is what not having free will entails. The parent didn't specify 'libertarian' or some other form of free will, and it's hard to specify what it means without resorting to handwaving.
The implied meaning I read was that if a person has no free will, there is no opportunity for them to change what they do. In truth, they are not free to change what they do, or even free to change what they will. Any appearance of such is an illusion.
If we accept that this is what not having a free will means, then it should be clear that, given we have no free will (our assumption from before), whether a person thinks that they have a free will or thinks that they do not have a free will makes no difference, as someone with no free will has no opportunity to change what they do.
Regardless of all that, I think kernel of the idea is a good one. Even if we are deterministic machines with no free will of any kind, we still experience out lives and should enjoy them. Thinking about if we have any oversight of our brain, able to determine the direction we want it to take is a foolish one, driven by the disconnect between what we experience and what we know about the mechanics of our minds. We are our brain, and everything else around it, and what it does is exactly what we are doing. We have the capacity to shape what we think and do as much as any other learning machine, but we are not an outside entity looking in.
My favourite quote about these ideas is this, and I have no idea where it comes from: "If nothing matters, then the statement 'nothing matters' doesn't matter, so you might as well forget about it and enjoy yourself."
I believe that gasses and suspended particles do have free will in the same way a brain running on the laws of physics has free will. You're asserting non-free will by appealing to intuitions around a simple example, but it is not justified.
Free will is at a different abstraction level to its implementation. Electrons cannot do arithmetic, but calculators can, with electrons as the implementation.
As an aside, your omission of "libertarian" from the quote of me suggests that you might be conflating two kinds of free will. Because you talk about free will without specifying the kind, the meaning of your reply is ambiguous. Hence, I have trouble agreeing or disagreeing with it. For what it is worth, I do not deny that compatibilist free will can have various degrees of freedom, where the degree is a function of the complexity and arrangement of the things it emerges from. For example, I do not deny that humans, dogs, and cats can be said to have compatibilist free will, nor that the human wills have more degrees of freedom than dog wills and cat wills.
If there is no free will, it doesn't matter. The payouts are the same regardless of what you do. You can't affect anything. The game is rigged, go home, good night.
However, if there is free will, the payouts vary drastically based on how you act, and the only way to get a good payout is to act as if there is free will.
So, acting as if there is free will is, at worst, one of the ways to get the there-is-no-free-will payout, and, at best, the only way to get the best possible there-is-free-will payout.
Note: If you mention Pascal's Wager in your response, you misunderstand the problem with Pascal's Wager. The problem with Pascal's Wager is that it does not give a way to determine which deity to believe in. The argument was constructed with reference to the Christian deity, but it applies equally well to Shiva or me, for example.
You can't abandon a whole methodology just because it can be misused.
http://en.wikipedia.org/wiki/Normal-form_game
http://rationalwiki.org/wiki/Pascal%27s_wager
http://plato.stanford.edu/entries/pascal-wager/