How many people penned the main Voynichese text?

[Koen G]

The usual assumption works when scribes use familiar scripts, that they have practiced writing for years. It's highly unlikely that the established well learned handwriting of a professional scribe will noticeably change over the course of a single manuscript, hence if there is a change in handwriting, usually another scribe is assumed.

I don't know if that's the case. As you said, a person's handwriting can change over time, and that's talking about the script that's most intimately familiar to them. But in manuscript descriptions, the assumption is not "this person aged", but rather "this was somebody else". That also tells us something about the way manuscripts were usually made: different scribes coming in was not an exception - it was quite normal.

However, when writing in a new unfamiliar script, it's expected that the handwriting will evolve and writing habits change as the hand adapts to the script. Interestingly, if I remember correctly the work of Lisa Fagin Davis, the most striking difference between the hands was in the execution of the gallows characters, the very characters that are highly specific to the Voynich script.

I understand that the VM is special and we cannot just apply regular expectations to it. However, it is my impression that hand 1, starting from f1r, already had a good feeling for the script and managed to maintain if for many pages. So I don't think we must necessarily assume that (1) they never wrote Voynichese anywhere else and (2) their handwriting, including size and ductus, would change noticeably after a period of absence.