It's a tiny throwaway detail, but Pol in Brightly Burning has the Mage-Gift and doesn't know it. He describes having the ability to 'sense energy fields' and says it's the rarest Gift he has. :) I figured he never set off the vrondi because he wasn't using magic, but only looking at it.

Iirc it says somewhere that the Vrondi-net expands as people use Truth Spell in new areas - I think it's in Winds of Fury, not sure.