Great post! I think, however, that when it comes to reading we just naturally imagine characters as being attractive before any description is given. Like one of the other commenters said, we tend to gravitate towards people who we find physically attractive, and so because we want to like these characters we imagine them as being physically appealing, unless the author has said otherwise. However, I think that's also why some people can be much more forgiving of 'evil' characters if they're attractive, which is a problem. Just because someone is hot doesn't mean they should quite literally get away with murder. Really interesting thought though!