Can rice be cooked in a double boiler?

I wouldn't recommend it, as I don't see any benefit in preventing the rice from coming in more direct contact with the heat. While it's true that (after the initial boil) rice is simmered at a low temperature for 15-20 minutes (depending on the grain), the rice still needs that direct, high heat in order to cook more quickly and evenly. From my understanding, double boilers are meant for cooking delicate ingredients that are easy to overheat or burn (that are more fragile than rice), such as melting and tempering chocolate, whipped eggs, and other delicate ingredients.