Was the paint added later? And is the artist also the scribe?

[Jorge_Stolfi]

So many people here don't even believe in different persons for A and B text?

I know of no reason to think that there might be more than one Author.  One person who knew the language devised the script (or the encryption, if you will), chose the material, and composed the draft of the text.  Whatever the origin theory, there are many possible explanations for the statistical differences between "language A" and "language B", that do not imply two different Authors.

There may have been more than one Scribe who copied the draft to vellum.  The size of the book makes that theory somewhat likely. It also makes it somewhat likely that the book was composed and scribed in installments separated by months or years; and this in turn makes it more likely that different scribes worked on each section.

On the other hand the drawings all look very much like the work of a single person; except for the Herbal, where there are no details that can be compared to the other sections.  As for the handwriting, while there may be significant differences between sections, the similarities are quite remarkable.  

One would expect that each new scribe would be trained by the Author on the alphabet, and would start working on the VMS only when the Author was satisfied that he could recognize the glyphs and copy them accordingly.   But I find it hard to believe that the Author also required that each new Scribe learned to imitate the handwriting and general sloppiness of the previous one...  

All the best, --stolfi