OOOO! I've an idea.
First, the quote from TDTCB and Mallahet:
"I have come, Emperor, so you might parlay with another."
Xerius blinked. "Who?"
For a moment, it seemed the Nail of Heaven flashed from the Cishaurim's brow.
So, no words, no glowing of the eyes or mouth (my bad).
Gnostic and anagogic sorcery are more bound to this world (through reason and metaphor), and so require the outspoken utteral as the portal through which will is made manifest.
BUT, the Psukhe, the passion-based sorcery, requires not an utteral and an inutteral, but a
conscious inutteral and a
subconscious inutteral. A perfect fusion of feeling and thought.
Perhaps, even, it is the utteral which stains the onta.