With that said, I'd like to reply further, becacuse I think you may be mixing up what we call hard problems of consciousness with easy problems of consciousness. Easy problems relate to things like correlations between the mental and the physical. The hard problems relate to things like how we would explain consciousness at all given, say, the tools the materialist has available. Your reply seems to muster evidence that relates to the easy problems but not the hard. I do not know of any kind of possible experiment researchers could be working on to address the hard problem.
I assume the author did not define consciousness because the problem they refer to is well known and discussed. When we talk about consciousness with respect to the mind/body problem, we're talking about the fact that there is an inner phenomenology, or a what-it's-like to be us. This kind of consciousness can be present while asleep, because it's not about the being awake and being aware, but rather the fact there is something that it's like to be you.
With that in mind, the examples you refer to with optical illusions, the man who mistook his wife as a hat, and so on, are all irrelevant to the hard question. There is absolutely no doubt that changes in the physical world can result in changes in the mental, including optical illusions -- the materialist, the dualist, and the idealist all agree on this point, and such examples will not settle the hard question. Our experiences are shaped, enormously, perhaps even as much as wholly, by our brain states. This is all part of the work of the easy problems of consciousness. None of that means or entails or suggests that the mental is an emergent property of the material, or that the material comes first.
An idealist of the sort I am will say something like this: God has in mind an idea of a physical world, and based on God's idea of that world (which includes God's idea of our brain) impresses upon other minds an experience of, say, a tree with leaves blowing in the wind. If my brain is wired differently, then I will have different experiences impressed upon me by God because of that than what others might experience. Perhaps the leaves of the tree will look a different colour to me than they do to others, all because of facts about my brain states (which themselves reduce to facts about an idea in God's mind).
The materialist has no way -- not even the vaguest hint of a way -- to explain the mental, the phenomenology of our consciousness. There is no explanation that can be given that says how we can go from the physical to the mental. The best that can be done are things like: deny the existence of any phenomenology/inner experiences altogether so that there's nothing to explain (or similarly -- literally identify brain states mental states and say they are the same thing), embrace some kind of non-reductive physicalism (which in my opinion amounts to a form of dualism), or hope that some clever person will come up with a better explanation one day.
Idealist views do not suffer from an an analogous "hard problem of non-consciousness". The idealist can give an explanation for the physical on their view, but the physicalist cannot give an explanation of the mental.