I had a girlfriend in college who wore both crop tops and knotted shirts. But I loved the knotted shirt look, because she was taking clothing that was originally designed to cover, and on purpose, altering it to reveal. My favorite was a long sleeve denim shirt that she wore in the cool/cold weather, with jeans. The only skin showing was a triangle of her belly (and maybe an inch or two around the sides & back), and she always tied the knot in a way that gave a clear & unobstructed view of her belly button. On a winter day or evening, the unexpected sighting of her bare navel was always more than welcome!