My Friend,
The secrets uncovered infiltrating the Calligraphers Guild are more mundane than expected. I prefer the bloodstains to inkstains any day, so next time send me somewhere I'm more likely to die from wounds than from handcramps. By Purity's Eye, if you ask me to draw another glyph...
The Darkest secret of the Guild is that the phonemes within a glyph can sometimes be deciphered. (Sorry to shatter your theories of dark rites and ancient moon dances) But glyphs aren't pronounced or read. They're memorised, and they change over time till the original collection of phonograms is almost unrecognisable. Take, for instance the glyph for storms: "zeras".
Contrast "zeras" with a glyph in its infancy: "zatalef," a bat like cephalopod the Alethi hadn't encountered until their recent conquests in Akak.
The glyph's phonemes are apparent as well as the glyph's resemblance to the actual creature.
Even older than "zeras" are the glyphs used in the First Oath of the Knights Radiant. These resemble more the complex, unreadable glyph representing the orders of knights than they do any middle or modern Alethi glyphs.
I suspect these were borrowed from an earlier source and incorporated into an already developing Alethi glyph lexicon.
This supports the claim that Alethi glyphs were adopted from older scripts likely descended from Dawnchant and might explain the two sets of phonemes used in glyph creation: Standard and Calligraphic.
Glyphmakers used both, the phonemes rotated, flipped and distorted to fit the calligrapher's vision. Next page: The Calligraphic Phoneme Set
