geoffreycaveney's Judaeo-Greek theory

[davidjackson]

In the parallel text Hebrew and Judaeo-Spanish book from which I posted a page earlier in this thread, it is striking that the Hebrew side has vowel diacritic dots but the Judaeo-Spanish side does not.

Not exactly. Judaeo-spanish (more formally known as ladino) is written in a variant Hebrew script known as Rashí. This script is phonological in style, with common letters for common vocal sounds, but the vocals can be repeated (two symbols for a, u, o and others depending upon their word position). 
Diacritics aren't used because they aren't needed. It's not an abjad. Spanish would be impossible to write in an abjad.