Many Voynicheros assume that the enciphering system of the VM treats the space between words as a particular character, like any other of the alphabet.
This is an attitude we have grown accustomed to, since we’ve grown up with computers, where the space has an ASCII code like the rest of “A” to “Z”, and before that the typewriter, where the space bar was a key similar to the others.
But it’s a fairly modern attitude. Until fairly recently, a space was just that — an empty gap between words, but not a character or symbol in its own right. (Even the venerable Engima cipher machine of WWII fame didn’t feature that character in its symbol set.) Rather, it was considered a part of visual design, like a line break (for with the Engima didn’t have a symbol either). Word breaks were useful to discriminate between word boundaries, but they contained no information in themselves. Throughout much of the middle ages, textswerewrittenassimplyalongsequenceofletters, and it was up to the reader to find the word breaks. (Compare this to modern typography, where it’s for the better part up to the reader to learn about stressed syllables etc.)
Even though this practice had pretty much ended by the presumed genesis of the VM (early 15th century), and word breaks were regularly used to increase readbility, I don’t think that any encipherer would already have thought of treating the spaces thus generated as particular characters which would be enciphered like regular letters. Hence, I also think it’s futile to search for such enciphering characteristics in the VM.