Can sulfates thin and damage curls? I think it's happening to mine
Sulfates themselves don't have that power. It may be drying your hair more causing breakage but prepoos or DC should solve that. I'm a 3b, I wash my hair twice per week with sulfate shampoos, I haven't seen any change in my curls.
It can, but tit depends on the product that you're using. Garneir can damage your hair because it has a lot of sulfates that can dry up your hair and thin your curls; look for products that are not high end products and have a lot of mosturizing ingredients like shea butter or coconut oil.
sulfate is not good for ethnic hair because we need moisture which sulfate dries hair. I'd suggest you switch your shampoo to a sulfate free one and your hair will feel and detangle way better.