I pretty much agree with this comment, until the end. At which point I still effectively agree, but think that there's disambiguation to be done.
I think that most people's concept of Free Will doesn't exist.
Physics constrains human action, and everything a material person does is in principle predictable, given precise measurements and knowledge of the laws of physics.
The concept of free will seems to be related to the idea of moral culpability. To the extent that I can still identify with myself even believing that I'm ultimately a collection of particles, I can hold myself and others responsible for our actions.
People don't try and predict what other people do by banging out physical calculations -- they try and predict other people by understanding them on a higher level of abstraction like psychology or empathy or trying to figure out what they think. This is just like a calculator. While it is ultimately a collection of particles, on a higher level it can be understood as a device that performs arithmetic.
It feels like Free Will exists because we don't try and predict people on the particle level, and our inner models of them seem to contain things like goals and volition. For example, if I pick up a rock and put it somewhere, it stays there until something else moves it. If I pick you up and put you somewhere, whether or not you stay there depends on whether or not you want to stay there. In order to accurately model you, I need to try and think about what you want to do, and hence I feel like you have Free Will.
If someone decides to punch someone else in the face, they can't say "Well, I was physically determined to do so" as a valid excuse. While that is true on the particle level, they are still a person who punches people in the face on the personal level.
If you decide to save children from a burning orphanage, it turns out that your particles are configured in a way that you go in and save children from a burning orphanage, and Physics makes that happen. You are still a good person who bravely saves children from a burning orphanage.
So while ultimately "Free Will" in the sense that people can literally do whatever and aren't ultimately bound by the laws of physics or something doesn't exist, people are still responsible for their actions, and are understood as acting in ways different from inanimate objects.