In a small bowl, combine 2 tablespoons of the olive oil with the vinegar, a little salt and pepper, and the salmon. Just before serving, put the shells on a baking sheet covered with crumpled aluminum foil so the shells stay flat. Preheat the broiler. Arrange the scallops in their shells and spoon on the smoked salmon mixture. Season lightly with salt and pepper and slide under the broiler for about 3 minutes, until the tops of the scallops turn opaque. Decorate each scallop with a tiny pinch of chives. Serve immediately.