I don't think that anything that has been through the digestive system is going to "taste fine." BrandenB has the right idea - cellulose largely passes undigested because we don't have the chemistry to use it as a food source. But vegetable fibers of all sorts are an essential part of our food - they give bulk to the feces as it passes through our gut and create the pressure we need to be able to expel undigested waste. The cellulose content of ANY vegetable or fruit will pass through the gut undigested.
I'm not sure on peanuts but corn can come out whole because its comprised of "cellulose," the fingernail s or skin of plants. Our bodies are not adapted to digest this like cows are so.. We simply don't.