The article talks about XBL (the binding part of XUL?): > There are hard to debug complications with binding lifecycles in our UI, and very few people know how

The article talks about XBL (the binding part of XUL?): > There are hard to debug complications with binding lifecycles in our UI, and very few people know how it works. > It adds enormous complexity to our platform in the frame constructor, style system, and the DOM implementation.