@kryan not relenting on the neg energy comment though :)
1. It's a commonly overlooked type of energy damage, *de facto*. The lack of immunity applies. Consider it contrary to Comp. Arc.'s *repair light damage*, which works on constructs (a type of object)
2. Can't you crit on an *inflict* spell, since it requires an attack roll? It doesn't fall under either of the two immunities listed for objects.
3. Only bludgeoning and slashing *weapon* damage typically damage objects. Spells may affect them normally, within each guideline