These are fascinating observations, thank you for sharing JKP!
Not to derail the discussion on tails but a few further comments about AEIOU.
As You are not allowed to view links.
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"In the notebook we can read in Frederick’s own hand that all the artworks and liturgical items he owned and the building projects he had initiated were to be marked with the vowel sequence (together with a framing loop)." [Emphasis mine]
Of course this is very interesting considering the gallows.
Another instance of AEIOU is in the Cathar chant You are not allowed to view links.
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Login to view., but there it is repeated throughout the song, whereas the Voynich vord only occurs once. Still I find this use interesting as it carries a rhythmic component which might relate to the dots above the vord.
There are possibly other uses too, this is just what a quick search turned up.