Many drugs induce unconsciousness, but these don't work by decreasing the complexity or organization of our brains. Doesn't this neatly refute the idea that consciousness is an "immanent property of highly organized pieces of matter, such as brains?"
Not really, because complexity can have an on-off switch: a global one, or at least a partial.
If you implement a software system that is conscious, but then suspend it to a storage device, and resume it one week later (so that it is surprised: where did the time go?) its complexity hasn't gone away. It just wasn't conscious for one week because it wasn't running.
Another thing to consider is this: there may be more than one consciousness in your brain! The one which is you, the one typing on Hackernews, is just the one which has access to the "console" so to speak: the fingers, the eyes, ... There could be other consciousnesses hidden in your brain that are suppressed. Like "background daemons". Maybe that part of the brain that regulates your body while you sleep (or don't sleep) is also conscious!
The consciousness-process which is "you" is deactivated during sleep, but the other background "daemons" remain conscious. (Clearly, sleep is not a complete, global shutdown of brain activity, in other words.)
(Also, I'm here reminded of dolphins which put half their brain to sleep at a time.)
I like your computer analogy because it's easy to reason about. Surely a powered-down computer is not conscious. So if consciousness has an off switch, then it's not immanent (inherent) to organization.
Koch compares consciousness to the electric charge of an electron. But the electric charge has no off switch!
