Preheat oven to 250°. Prick potatoes all over with a fork or sharp knife and wrap tightly in foil. Bake until soft, about 1 hour.
Unwrap potatoes and cut lengthwise slits in the top of each. Carefully scoop out flesh from center of each potato into a medium bowl, then add butter, sour cream, chives, green onion whites, half the cheddar, and half the bacon. Season with salt and pepper.
Spoon filling back into each potato, mounding it on top. Sprinkle with remaining cheese and return to oven until melted, about 5 minutes. Top with scallion greens and remaining bacon.
