Dazes that are converted to stuns by Confounding Suggestions do not work correctly with this sigil. In fact, they actually last significantly less time than converted dazes while the sigil is not used.
Relatedly, the duration bonuses from these two sources do not stack for regular stuns (tested with signet of domination), though this could certainly be intended functionality, it is not listed in the wiki, and so is mentioned for completeness.
The other aspects of the Confounding Suggestions trait all seem to be functioning as intended, and we tested them into the ground in all combinations we could consider tonight.