This is why the Merchant Class and Sea Elves in BECMI Mystara are so OP
1: The reaction System
If you're using the old B/X reaction roll system, there is only a one-in-thirty-six chance that any given monster encounter goes straight to violence. Anything else gives you some room to manoeuvre: to talk, bluff, make a bargain, offer a bribe, whatever. If you want a fight you can have one, but you almost never actually have to fight. (And hell, even if they do attack, you can always just run away.) This is very different to later editions of D&D, which assumed that monsters would always attack on sight and usually fight to the death.
If you use the reaction system, then instead of the dungeon becoming a series of tactical combat challenges, it becomes a network of social challenges. What does each group want? What does it need? What can you offer them, and what can they offer you? With a bit of quick thinking and a lot of heart, you can talk your way through a dungeon much more effectively than you could ever fight your way through it.
The power of having the Darokin Diplomatic Corps Badge is not to be understimated. Yes I have authority to negotiate a trade treaty.