An Architecht isn't using common sense, she/he is using a great amount of knowledge to make sure that building doesn't fall down, and the same goes for designers. What we are doing may seem like common sense to the end user, but the knowledge it took to get to that point is far from common.
Thanks for your comment. I completely agree with you. Maybe I wasn't too clear in the article (I hope I was), but that's the point I'm trying to make. Our, along with the architect's, experiences in our field allows us to apply principles to our work that seem like common sense to everyone. But common sense is acquired through experience and years of learning. To others, it may seem like common sense but it's only because they don't see the work behind it.
Thanks for reading!