Why and how the text could be Bavarian

[Stefan Wirtz_2]

[..] But the above argument is not good.  

The "double consonants" of German and Italian are just a spelling convention, to indicate sounds that are not "double consonants" at all. [..]

This "spelling conventions" did not come suddenly after 1438 or whenever VMS was finished. You will find lots of German writing of 15th, 14th or 13th century showing masses of double consonants without any conventions, sometimes even changing whitin the text from one and the same author.
German has many roots in Latin where geminized consonants were a standard and standardized by finalisation of Latin at least 1,000 years before VMS.
I don't have to point out the meaning of Latin for Italian and all it's subforms.
There was never a time until ~1450AD showing central european texts without any doubled characters -- there are a few doubled also in VMS, but almost all in a kind of fixed comibinations. By numbers, not even coming close to those Latin, German or whatever in western europe.

We had the double-consonants-discussion already about Venetian: it leaded to a moment when I just posted random screenshots of Venetian texts showing dense appearances of Geminis, while you insisted that there are no doublings at all in this language.
Ended with "there are a few doubled consonants in Venetian" at last.

But in Voynichese, there are such double appearances nearly next to zero.

About "Bavarian":
yes, that's very convenient to locate VMS at our southern not-quite-german-anymore-but-still-not-austrian neighbors; they are notorious for their guttural grunting, but I never heared about a try to write that down (encpihered! In a personal shorthand!) until Karl Valentin and Fredl Fesl...
Yes, it is convenient to enhance the unconventional spelling of beginning of 15th Ct to a local dialect with nearly random pronounciation and spelling, that leaves enough room for "interpretations" of those harmless-looking Voynichese characters -- but that's already where the tar pit begins.