Given that stacking attack bonuses has much greater impact than stacking damage bonuses, it's surprising that Blade Opportunist, Combat Reflexes, and Nimble Blade, are all untyped, and so do stack. Indeed, almost every attack bonus in the PHB feats is untyped, whereas all the damage bonuses are feat bonuses. It should be more like the opposite.
Smeelbo
Yes, but most of the attack bonus feats are conditional (when you make OAs, when you have combat advantage, etc.), whereas most of the damage bonuses are universal. That's the key difference.