Although unsalted butter is preferred, one can make clarified butter from either unsalted or salted, as long as it is understood that the result with salted will be different, which may or may not be acceptable to the user, and will certainly impact the salt level contained in the remainder of the recipe. I, too, would like to see some reliable information substantiating the claims that "milk solids help form the barrier between the food and the pan", and that "salt helps too" re: preventing food from sticking. I'm not seeing how lactose (milk sugar) and casein (milk protein), or salt, would be helpful in that regard.