A lot of the behaviors should just have a toggle to turn them off. For example, there are many situations where margin collapsing is in the way and I keep wondering why there isn't simply a `margin-collapse: none`. It would also be nice to have something like `default-styles: none` that will remove all the default styling for h1/h2/etc. and em/strong/cite/etc. so I don't have to deal with browsers having differing defaults.