I believe that month names in the zodiac section were likely added by someone who couldn't read the text: the fact that the only clearly readable labels are paired with the only clearly recognizable images looks like a significant coincidence.
On the other hand, the three sets of marginalia in which the Latin alphabet is used together with Voynichese appear to be signs of actual usage of the manuscript by someone who could read and write Voynichese: You are not allowed to view links. Register or Login to view., You are not allowed to view links. Register or Login to view. and You are not allowed to view links. Register or Login to view. . Two of the three (66r and 116v) include illustrations with figures similar to Voynich "nymphs". You are not allowed to view links. Register or Login to view. doesn't seem to be much later than the carbon dating of the ms. Overall, it is not clear if these marginalia were produced by the same person (or one of the persons) who produced the main body of the manuscript.
On the other hand, the three sets of marginalia in which the Latin alphabet is used together with Voynichese appear to be signs of actual usage of the manuscript by someone who could read and write Voynichese: You are not allowed to view links. Register or Login to view., You are not allowed to view links. Register or Login to view. and You are not allowed to view links. Register or Login to view. . Two of the three (66r and 116v) include illustrations with figures similar to Voynich "nymphs". You are not allowed to view links. Register or Login to view. doesn't seem to be much later than the carbon dating of the ms. Overall, it is not clear if these marginalia were produced by the same person (or one of the persons) who produced the main body of the manuscript.