How many people penned the main Voynichese text?

[MarcoP]

If someone wrote the Manuscript in bursts, over the course of decades, that could also plausibly explain the variations in topics ("languages") and handwriting style.

I am also of that opinion.

Again, this is possible. But why would this explanation be preferred over the usual assumption in manuscript descriptions that different hands = different people?

To me, the most attractive reason is the correlation with the different languages. In particular, the fact that Scribe 1 produced different languages in most Herbal A pages and Pharma/Small-Plants pages.
I think it is particularly interesting that, You are not allowed to view links. Register or Login to view., Herbal A pages that were bound next to Pharma pages use a language that is intermediate between the main Herbal A body and Pharma.
Bigram-frequency plots from You are not allowed to view links. Register or Login to view., left labelled by scribe, right labelled by folio.

   

From this, I understand that the language drift is not due to different scribes nor to different subjects (if we take illustrations as defining subjects, we have Herbal pages with Small-Plants language, so the illustrations do not explain the language change).
Evidence of an evolution process affecting the production of Scribe 1 treating a single subject (Herbal) suggests to me that something similar could underlie the whole “language” drift. The plots above are somehow ambiguous, but they can be read as a single >-shaped trajectory (though it’s also possible to see slightly separated clusters largely corresponding to scribes and subjects).


It could be that differences in the script and differences in language are entirely independent from each other, but still I find the idea of a single “drifting” process attractive. This is one of the many cases in which I have an opinion but I don’t trust it. I think it’s likely that Lisa and Colin’s announced paper will add to our knowledge of the subject.