I'm also getting a sense for how poetic forms change. Some people think that a poetic form, especially haiku, has to be rigid. But haiku started out as a piece of another poetic form (renga, a collaborative form). That form has all sorts of rules. But it started as a rejection of another form that was even more formal. So people are always taking a form that feels formal to them and loosening it and then that form solidifies and becomes the basis for something else that loosens it. So it forms a chain of links stretching back into the past.