1. Preheat a covered gas grill to high. Bring vinegar to a boil in a small saucepan over high heat. Boil rapidly until reduced to about 1/2 cup, about 12 minutes.
2. Cut baby eggplants in half lengthwise, leaving stems attached. Use a small knife to score flesh in a crisscross pattern.
3. When sauce has reduced, remove from heat and stir in honey and olive oil. Brush the flesh side of each eggplant half liberally with glaze and season generously with salt and pepper. (If using larger eggplants, brush and season both sides of slices.)
4. Oil grill well, and place eggplants, flesh side down, on grill; turn off burner directly underneath. Turn other burners to medium. Close lid. Cook eggplants for 10 to 12 minutes, turning once. When done, eggplants will be lightly charred and easily pierced with a knife. Brush with more glaze and season generously with salt and pepper. Serve warm or at room temperature.