Heat a grill or grill pan to medium-high. In a small bowl, combine the soy sauce, honey, five-spice powder, and 1/4 teaspoon pepper for the sauce.
Season the pork chops with 1 teaspoon salt and 1/4 teaspoon pepper. Grill for 10 minutes, turning once. Using a brush, baste the chops with the sauce and grill until cooked through, about 2 minutes more.
Meanwhile, toss the plums and scallions in the oil. Grill the plums for 5 minutes, turning occasionally. Grill the scallions for 2 minutes. Divide the pork chops among individual plates and serve with the plums and scallions. Drizzle with the extra sauce.
Shortcut: Use boneless pork chops to halve the cooking time.