Aanother statistical take on Voynichese

[kostrubaty]

I'm not sure order-3 Markov chain is "simple". Can you explain how would the XV century scribes implement it? For starters, this requires some well designed state transitions, and a lot (thousands?) of them. It's one thing to approximate some sequence of characters using a Markov chain, it's a different thing to explain how this sequence of characters was produced.

Also, your generated sample, which you describe as "indistinguishable from Voynichese to the eye" appears a bit odd to me:

qoeeal shd shos lsheodain oteedy dchdar ol ar okold qokal qopchdy or olkchy qokeey yteey otair deeol shar chedy chor ykodaiin

It's reasonably good, which is of little surprise given the order-3 Markov chain, however I don't think qoeeal looks very plausible (it doesn't appear in the MS), and neither does lsheodain or ykodaiin, though they look less iffy, while okold doesn't appear as a standalone word, dchdar is quite rare, deeol only appears once as a standalone word and once as a prefix. So, to my eye this looks like very unlikely Voynichese, because it's packed with rare and unusual words.

Well if you look at the values the entropy is ~2 that means that characters are chosen from very limited pool, this means that given a character you only have 2 options to choose for the next one. They could have used some form of volvelle with cuotouts, but it can be just a simple flow diagram.
As for indistinguishable -> It simply means that given 2 text excerpts one in voynichese one generated you're unable to tell which is which. You're able to tell only because you've checked with known text. If I were to say here's a new text I found in this language you could not objectively prove/disprove my claim basing your judgment solely on the text itself.

This actually neatly explains why is the structure like this, they probably prepared the cartouches by prefilling first letter of each line. 
Then scribe would use the diagram to look up the text and write it down letter by letter. 

Other characteristics like self repetition are simply caused by human error. Imagine sitting in a dim workshop writing down sequences of nonsensical letters. At some point you'll just start repeating the words sometimes just to avoid looking them up on the diagram. 

This also explains how 5 different authors could produce text with exactly same statistical fingerprint which is unrealistic even if we assume it's a translation of a source material.