Beautiful topic! I would like to add something:
Some npcs may answer diferently based on an item you are carrying/wearing, for example:

Vladruc, the vampire on top of magic store in venore.
If you try to talk to him while carrying a Garlic necklace he dosen’t answer you right. He just  answer some pre-fixed phrase to every thing you say.

Maybe some NPCs will only answer you something you want if you have an Item?