my suggestion about the author of MV

[Anton]

If the VMS is inherently deceptive about the nature of the text, either because it is strongly coded or encrypted (an anachronism in the 15th century), or because it represents something else than language, then everything else prima facie about the VMS (an otherwise unremarkable herbal/astrological/medicinal manuscript) is probably nothing but deception and misdirection too.

I don't see how that would follow from the fact that the text is not a plain text. Imagine you are a learned person of 15th century, and your income in a competitive market relies upon your knowledge, and upon your knowledge not being disclosed to others. (Pretty same thing as it is still today, only that there was no file encryption back then.) Some pieces of information can be represented in text, some pieces you have to put in graphical form. The text you can protect (through some secret encoding procedure, or through using your own synthetical language), the images you cannot.

What though there are hints about the subject? Everybody knows that you are a medical man and an astrologer. You won't hide that, and you will not, because that's what brings you money. What you'd like to hide are exact pieces of knowledge, so that if your fellow astrologer crushes your skull and steals your book, he is not able to make use of it. You generally won't care about researchers half a millennium since, and (to be honest) even those cannot boast much success up to date