I talked about the issue of every npc being killable with another friend of mine and he did convince me of the value of having every npc be killable-even though it still feels like a bizarre thing to care about to me, I get why people care about it and I see the value it can add to a game, at least hypothetically. But the way he put it that sold it to me is that you absolutely should get locked out of stuff if you kill the wrong npc, even get cut out of the main questline as punishment for doing something obviously stupid. I disagree with the idea that you should be able to do everything even if you kill important npcs. There should probably be some give, but I fully think there should be a point where you fail the quest and the game throws its hands up and says no, you can't continue, you've ruined things for yourself.
I don't think that this should really be a priority for devs, and I do have concerns that working around making everyone killable could potentially be a detriment to the variety of stories being told.
