And that is exactly the central paradigmatic issue that is challenged by this paper. The reviewers, and apparently the editor too, assume that even if the neural vehicles were to actually be round (which the reviewers strongly doubt), there is no guarantee that the subjective experience of those neural vehicles, i.e. the phenomenal contents, are necessarily round also.

But that is only their paradigmatic assumption. Nobody has ever demonstrated that the shape of the phenomenal contents are necessarily different from the shape of the neural vehicles that produce that phenomenal content. Or even that they are distinct entities at all. It is at least equally likely prima facie that the neural vehicles are not only isomorphic with, but identically equal to their contents.

If identity theory happens to be right, then your argument is like saying that George W. Bush might be round, but it is not at all clear that the President of the United States is also round. Until the reviewers can demonstrate beyond a reasonable doubt that the neural vehicles cannot possibly be identical to their phenomenal contents, identity theory remains at least as likely (and by far the more parsimonious explanation) as the alternative that Dennett proposes, that the neural vehicles need not resemble their phenomenal contents.

But even if Dennett were right, that would only open the next unanswerable question, which is that if phenomenology is completely independent from physiology, then, in Koffka's classical words, "why do things look as they do?" Whenever perception is veridical, one can almost believe the naive realist answer that "things look as they do because they are what they are". But the void of the sky is not dome-shaped, as it appears phenomenally, and distant objects are not smaller, as they appear perceptually, and phenomenal colors are not what they are chromatically, as they appear perceptually, and the world observed in dreams and hallucinations does not exist objectively, as it appears subjectively. So things do not look as they do because they are what they are, they look as they do because that is how they are represented in the brain!

Your whole argument is based on the assumption that supervenience, and vehicle/content distinction are an established fact, rather than merely a paradigmatic hypothesis. The whole point of the present paper is that this is not at all necessarily the case, and that it is at least equally likely that the neural vehicles are necessarily and inevitably identical to the phenomenal contents. In other words, the world we see around us is not the real world itself, but merely an internal perceptual replica of that world constructed by neural processes based on sensory input. I recognize that that is a big one to swallow. I'm not asking you to accept identity theory as your personal philosophy, but merely to admit that it is a valid alternative hypothesis that deserves to be released to the larger community to allow individual researchers to make up their own minds on the issue, even if you yourself remain unconvinced.