Preheat a grill pan over medium-high heat. Add the limes cut-side down and cook until deeply charred, 5 to 8 minutes.
In a mixing bowl, whisk together the olive oil, rice vinegar, honey, grated ginger, soy sauce and fish sauce. Season with salt and pepper, then set aside.
Add the frying oil to a cast-iron skillet large enough so the oil comes no more than halfway up the skillet sides. Heat the oil over medium-high heat. Add the jalapeno and 2-inch piece ginger to the oil.
Place the fish on a cutting board and pat dry with paper towels. Make slashes crosswise on a diagonal along the body of the fish every 2 inches on both sides, cutting all the way down to the bone. Season the fish generously inside and out with salt. Mix together the rice flour, coriander, lime zest and 1 tablespoon salt in a shallow bowl. Dredge the fish in the seasoned rice flour.
When the oil is 350 degrees F, grip a fish firmly by the tail and carefully lower head-first into the skillet, making sure to lay it down away from you. Repeat with the other fish. Fry until the flesh on the bottom side is cooked through and the skin is deeply browned and crisp, about 4 minutes. While the fish are frying, baste the inside of the heads with hot oil periodically.
Use tongs and a fish spatula to carefully turn both fish over. Fry until the flesh on the second side is cooked through and the skin is deeply browned and crisp, about 4 minutes. Transfer to a wire rack and season both sides with more salt.
To serve: Place both fish on a platter. Spoon the ginger vinaigrette over the top and around the fish. Garnish with cilantro and scallions and place the grilled limes around the edges.