Heat oil in a heavy-bottomed pot over medium heat. Add onion, celery and carrots and sauté until softened, about ten minutes.
Add lentils, broth, water, salt, garlic, cumin and coriander. Stir together and bring to a boil.
Once soup has reached a boil, reduce heat to low and simmer, covered for 20 minutes.
Add chopped potatoes and simmer, covered for 15 more minutes or until potatoes are fork tender.
Add kale and simmer, covered for 5 more minutes, or until kale is wilted.
Remove from heat and stir in red wine vinegar. Season to taste with salt and pepper.