> The human brain is a finite, physical thing. It can't store an infinite amount of data.
True, but it doesn't really detract from his statement because do we really know what that upper bound even is? I don't think we come close to the theoretical storage limit... So saying "every memory you have is permanently stored" is effectively true, at least true enough for a thought experiment like this. Perhaps when people live to be 200 years old and we know more about the brain we can test this, though.
I used to be weary of learning new, complex things, thinking I'd "lose" old knowledge XD
> I don't think we come close to the theoretical storage limit
That was the point of the second part of my comment--which the person I was responding to said was not relevant to what he meant.