Preheat the oven to 425 degrees F. Line a baking sheet with foil.
Prick the potatoes all over with a fork. Place on a plate, put in the microwave and cook until a knife can easily be inserted, flipping halfway through, about 14 minutes.
Meanwhile, toss the chicken with 1/2 cup of the Buffalo sauce, half the pepper jack cheese and the garlic powder in a medium bowl.
Cut the potatoes in half lengthwise and scoop out the flesh into a medium bowl, taking care to keep the skins intact (if the potato is too hot, use a clean kitchen towel to hold). Place the skins on the prepared baking sheet.
Mash the potato flesh with the cream cheese, 1/2 cup of the Buffalo chicken and the remaining 1/4 cup Buffalo-style sauce. Stuff the skins with the mashed sweet potatoes, and then top each skin with the remaining Buffalo chicken. Sprinkle with the remaining cheese and bake until the cheese is melted, about 5 minutes.
Meanwhile, mix the celery with the cilantro leaves in a small bowl. Top each potato with the celery salad and drizzle with the ranch dressing.