As far as I'm aware the silly issue with extra dice being added after the unconscious non-leathal cut off, and thus automatically killing anything you non-lethal, is still an issue. So, if you have weapons or abilities adding extra dice of damage to your melee attack, you functionally cannot do things non-lethally anyway, unless the damage is just perfect to put them to the 0 threshold with the very last damage die you roll. It's been a thing almost since non-lethal damage was put in in early EA, never fixed as far as I know.