Before this can be a meaningful discussion, the participants must be clear about the definition of "you". Otherwise we're up against a forever morphing concept, like God, that changes on a whim because it's undefined. The statement "... who you are is completely determined by the physical state of your brain" (Drosera #28) cuts close to the bone, but only if taken in the sense that the state of your brain is you.

To accept free will as reality, you'd have to assume there is an uncaused "you" who can choose between alternatives and yet not be affected either by the environment or the consequences of your choices. This is the basis of body/mind duality that we all know doesn't hold up too well even under the influence of a remarkably small volume of alcohol.

Maybe this sounds like Buddhism to some, but not defining the concept of "you" is apt to lead to a place firmly in the territory of the Christian concept of soul.