Bug is fixed in the playground. Thanks again for catching it!
It gave me some ideas to make routing better, too. For example, maybe you don't want the edge to curve above, but rather below. Or, in more complex examples, maybe you want the edge to curve above one thing and to the right of another.
(will update npm shortly too)
This is just for me, but I don't think I want to get into the business of specifying placement in that much detail. It would too cumbersome and I'd rather focus on what I want the diagram to convey, rather than how.