Split brain surgery shows us that two consciousness can and do exist in the patients. So why would you think that disease or disorder would not be capable of that?

I find that utterly unremarkable.

From the source paper " I propose an idealist ontology . . .summarized as follows: there is only cosmic consciousness. We, as well as all other living organisms, are but dissociated alters of cosmic consciousness, surrounded by its thoughts. The inanimate world we see around us is the extrinsic appearance of these thoughts. The living organisms we share the world with are the extrinsic appearances of other dissociated alters."

That is a very large leap of faith from brain issues that alter consciousness in ways we do not fully understand.

Bernardo Kastrup
"Independent Scholar" (his description not mine)
From his own website

My work has been leading the modern renaissance of metaphysical idealism, the notion that reality is essentially mental. I hold a Ph.D. in philosophy (ontology, philosophy of mind) and another Ph.D. in computer engineering (reconfigurable computing, artificial intelligence).

On peer reviews of his work, again from his own web site

I have had mixed experiences with reviewers so far. On the positive side, one of the three accepted papers has been much improved by critical and extremely thoughtful reviews at SAGE Open, a journal I now consider a prime example of high professionalism in publishing.

( Please note Sage open is just that a self publishing site for academic journals, NOT a peer reviewed publisher of same anyone can contribute and review it is basically an an amateur scientists face book.)

I also had a rejection by Neuroscience of Consciousness that was worth more than an acceptance: although my submission was considered not to match the journal's focus,

There have been less fortunate examples, though. Another paper of mine was rejected by AIMS Neuroscience on the basis of a single reviewer report,

There is one journal, however, whose treatment of my submission has made me feel so disrespected that I want to share details with you. The journal is Metaphysica.

( METAPHYSICA: International Journal for Ontology and Metaphysics. is a semi annual journal publication of academic Philosophy NOT science as the other journals mentioned are)

• "With regret, I must inform you that your submission cannot be accepted for publication in METAPHYSICA: International Journal for Ontology and Metaphysics. Please find below the referee’s" report.
  Reviewer 1
  I recommend rejection because the paper does not present sufficient quality for the journal.

• The above is the complete reviewer report. I did not edit or shorten it; this is all there was to it.
  Apparently, a complete review of a 9000+ word manuscript had somehow been started and completed overnight ...for a journal that sat on my manuscript for 9 weeks. *

This guy actually boast about the prestigious journals he has been REJECTED by on his own site and boast about self publish works.

to be fair
Has written a few books on new age bullshit including the oxymoronic "Rationalist Spirituality," "An Ontological Solution to the Mind-Body Problem", and "The Idealist View of Consciousness After Death"

So about neuroscience and the functions of the the diseases of the human brain, this person knows about as much as I do.

An interesting hypothesis. I don't quite see how it makes the problem of consciousness any less hard; it just pushes it out one remove, then you have the same old problem of infinite regress. An interesting read, at any rate.

I'm beginning to think we try to rebuild the universe as we understand it inside our head. As our awareness increases through more information (from the senses and memory) and our understanding of the paradigm rules increases then our objectivity and awareness increases.