If I'm reading this right Iroran clerics and Paladins can boost fist damage to 1d6 via the Deific Weapon class feature or Deadly Simplicity class feat.
But there's no mention of being able to deal lethal damage with fists or other nonlethal weapons in those abilities. The old Improved Unarmed Strike general feat which would have fixed that is gone.
This feels like an oversight. Any chance of clarification in the FAQ and the final rulebook?