A good match, perhaps from the Zürich area...

[davidma]

As one who has nearly zero experience parsing medieval handwriting, I find the matches in this thread extremely convincing. Supposing the authors of the marginalia and the authors of the manuscript shared the same time and geographical location, how does this affect the list of possible plaintext languages for the manuscript itself?

I agree, I think given the rarity of the final 8 for s, as well as the distinctive letter shapes, I would be extremely surprised if it turned out that this marginalia (and hence the rest of the VM) wasn't a product of someone who lived in or around Zurich/Northern Switzerland/Southern Germany between 1410 and 1450. What I find really interesting is that this also gives extra context to the other bits of plaintext in the VM, i.e. the months name. There is another thread with a lot of archival work that pretty confidently places the month names as originating from somewhere in N.E. France (specifically either Lorraine or Picardie due to the rare and specific regional spelling of Octembre and the clear germanic influences in Augst, though I feel this is already speculation on my part ). Cambresis and Lorraine were all part of the HRE up until the 1550s, so I do not find it unlikely that the VM could've traveled as far as 500km from Zurich to Cambrai. 

In any case, these are extremely interesting findings and another crucial piece of the VM puzzle. It would be amazing to have a bit more clarity on the pre-1600s history of the VM, or even a potential origin date and place!