Bring a pot of water to a boil over medium-high heat. Add a pinch of salt and the pasta. Cook according to the package directions. Drain, then rinse under cool water until the pasta is no longer warm.
Meanwhile, fill a bowl with cool water and ice cubes. Set up a steamer basket in a pot over barely bubbling water (medium heat).
Cut each broccoli crown into 4 or 5 pieces. Place them in the steamer, cover and cook for 3 minutes. Immediately transfer the broccoli to the ice-water bath; let it sit for 5 minutes. Drain, and cut the broccoli into 1/2-inch pieces.
Whisk together the vinegar, mustard, chives, parsley and sugar in a liquid measuring cup. Season with salt and pepper to taste. While whisking, slowly pour in the oil to form an emulsified dressing. Taste, and adjust the seasoning as needed.
Combine the ditalini, broccoli, corn, onion and bell pepper in a large bowl. Add the dressing and toss to coat evenly. Let sit for 15 minutes before serving. Toss one last time and serve.