I see this was from three days ago but the hot algorithm has dug it back up, so I'll give my take on it anyway.

Yeah, under many worlds, the universe is completely deterministic, but the human brain trying to make sense of the experience of living through the branching process views the universe differently. This leads to the invention of classical physics, and also to quantum observations appearing to be non-deterministic. I think you could talk about free will in the context of physics and the fundamental nature of the universe, but most people care about it more in the sense of our daily interactions with other people. I think the biggest factor that separates these is the vast amount of information and information processing that is needed to be able to actually treat something on the scale of a biological organism as deterministic, so even if the universe is deterministic, you can be essentially certain that you will never in your life meet any person or entity that could exploit determinism, so in terms of how you make decisions, you can ignore it. Physics can tell us that no information can be created or destroyed inside a thinking brain, but in the experience of living life as a human, for practical reasons, we have to accept the idea that peoples minds can be completely original sources of new ideas.