There's probably a hard limit to how much you can know about consciousness in general. Say, for instance, that what IIT measures isn't consciousness but memory

There's probably a hard limit to how much you can know about consciousness in general. Say, for instance, that what IIT measures isn't consciousness but memory. It tells you that when you take general anesthetic, the IIT measure in the brain decreases. But it's hypothetically speaking possible that when you get anesthesized, you're still aware and feel everything that's happening to you (in the sense of having qualia), only that it never gets recorded to memory. The result is the same: it appears, in retrospect, that you lost consciousness. But you can't prove that you actually did, only that your memory of the past behaves as if you did. This seems fundamental, unless we through some future discovery can nail down what consciousness is. The consciousness-status of past me is just as opaque as that of other people.