The description does say that it is EXTRA damage. So that would lead me to think it should be in addition to what the weapon already does.
For some reason I can't explain right now, I think this is how NWN handles extra bonuses. They aren't meant to stack due to mechanics. No proof though, just a shadowy recollection of some thread I might have read once.
Yeah I recall this as well but I would need to search to find it.Does it over write the enchantment bonus (fire, cold...)?Ok I can see why it would over write the piercing damage. But it should not over write the to hit bonus.