Well, you quote Dave C above as saying 'we can use the knowledge argument to compellingly establish the failure of logical supervenience,' Suppose he is right.
Then it's possible that something be physically identically similar to Mary Ordinary when she at last sees a ripe tomato, without having any experiences.
Either that argument works or it doesn't. If it does, then Mary Z is that somebody. That is, she realizes that very possibility. It follows that she doesn't learn
what experiencing red is like when she looks at a ripe tomato,, since she has no such experience. . It seems to me that IF the knowledge argument
is sound, we can pretty easily go this far.

The question remains, how do we describe Mary Z and what she DOES do? Here I think we have decisions to make. We might say that she is never conscious, that when
she wakes from sleep she doesn't become conscious of her surroundings. This requires insisting that a physical system must have experiences to
be conscious. I prefer to talk as though experiences aren't required for 'consciousness of,' so I would prefer to say that Mary Z does become conscious of her surroundings.
So I would say that any system that is causally responsive in some detail to its surroundings is 'conscious.' If we have a radar alarm system that
detects intruders, and we switch it on and it starts beeping,  I'm willing to say it now is AWARE of intruders. But not because I think it's having
experiences. I just figure it's chauvinistic to insist that something must have experiences to be aware of (or conscious of) its surroundings.  I'm not into packing a lot of human
psychology into such terms.

So I would say that Dave's zombies see things, hear things,
smell things, are conscious of things. They just go about it without having experiences, I don't think my inclination to say this provides any reason
to think Dave's zombies are impossible. Of course, there may be other reasons to think they are impossible.

I really think the Knowledge Argument is doing a lot of work here. Best, Jim