In the past there have been those who have chosen to side with the taint, yes. The Harlequin are usually the ones who hunt them down, but some do escape into the tainted lands. They are few and far between, but there have been succesful "double agents" on Ashes yes. Most people just see them as insane and corrupted by taint- which is the case with some. As for witchcraft lore or superstition; not nearly no. That's where the temple of fire's 'inquisitions' come into play. Anyone who doesn't worship the flame within the nation of Ashes is deemed a heretic and hunted by the Knights of Flame.

Of course, hiding the superstitions/lore is much easier to hide than betraying Ashes.

The Harlequin are v e r y good at their jobs