Don't shoot the messenger. I'm not the one who decided that shell is less formal than calf. I'm also not saying that your point isn't perfectly valid, because it is. I can see the logic behind why the heavier rolls that shell develops instead of creases, and the more hefty look that shell has (it almost looks chewy, like caramel, for lack of a better word) would make it less formal on average. However, I'm no stranger to seeing shell shoes that look like they could be worn to a black tie event as well. I'm just reporting the general opinion.