I guess palm oil is different than coconut oil? Coconut oil is supposed to be very healthy, and is partially hydrogenated I believe, so would keep well. But other manufacturers (horrible way to talk about food) have found ways to take the trans fats out of their products, why can't Nutella take the palm oil out of theirs?
Palm nuts are grown specifically for their oil. Not the same as coconut. Huge swaths of places like Paupa New Guniea have been stripped and planted with the palm monoculture product. Nasty business. Not to mention what it does when you eat it.
Recently we've been found to have a yet undiscovered sense of taste - sweet, salty, spicy, bitter . . . and fatty. Palm oil tastes different than peanut oil or olive oil - in it's fat content. If they replaced it, the product would taste different.