And yes, I agree that the Book of Vile Darkness is laughably simplistic. The line I'm referring to went something like this:
"In a world where good and evil are concrete things, sacrificing yourself to help someone else is a good act. Exploiting someone else for your own benefit is an evil act. It's a high standard, but that's the way it is."
He then proceeds to jump through hoops for 200 pages to explain why, in this world of concrete good and evil, PCs can murder monsters for their gold and still themselves BE "good." That's only because to do otherwise treads on the genre conceits of the game.
IMO, a lot of what evil and good are is probably best not decided by the player, the DM, nor Monte Cook, but rather through the eyes of some NPCs...namely, the gods. It's their
job to judge mortals, right? For the actions of a PC or NPC, judge what the deity they worship or pay lip service to would think of what they've done....in other words, ask, "what would Crom think?" It's a big ask to get NPCs to do rules-affecting stuff, but hey, they're
gods.
To me, the attractive thing about this solution is that what is good to a LG god of protection and chivalric warfare is going to likely be somewhat different on the details in their view of what is good to that of a LG god of self-sacrifice and non-violence. Who gets the deciding vote on whether that act just then was evil, or merely the actions of a reasonable person in an unreasonable world? The deity closest to the worship of the character.
(A couple of caveats: If the character doesn't have a deity, or is some mindless creature, there's probably a god assigned the portfolio of judging them - like in FR where there's a plane the dead go to if they're nonbelievers. If they're some peasant who prays to the rain god for rain, the protection god for protection etc. determine the deity most relevant to the situation at hand, and ask their opinion.)
"The Walruses are coming!"
QFT