Sauté the onion in a large dutch oven or heavy bottomed pot in a little bit of oil over medium heat. (You can dry sauté covered with a lid to prevent sticking for an oil-free soup)
Cook until soft, then add garlic, celery, potatoes, and red pepper, reserving some diced red pepper for garnish.
Stir in the spices. Don't worry about things sticking to the bottom. Cook until the potatoes are slightly softened, about 5 minutes.
Slice kernels off the corn and add, raw, to the pot along with the vinegar, vegetable broth and coconut milk.
Cover and gently simmer until potatoes are tender, about 15 more minutes. Transfer half of the soup to a blender or blend partially with an immersion blender. Blend until creamy then return it back to the pot and stir.
Garnish with the reserved red pepper, some cooked or frozen corn kernels (optional), and chopped chives.