I'm not 100% sure about this change. The [JCR documentation](http://www.day.com/specs/jcr/2.0/10_Writing.html#10.8%20Cloning%20and%20Updating%20Nodes) states that "The clone method clones both referenceable and non-referenceable nodes", but it doesn't explicitly says how "removeExisting=true" should behave for non-referenceable nodes.

From our discussion on the [symfony-cmf-devs list](https://groups.google.com/d/msg/symfony-cmf-devs/Ro12vnxInG8/gj94zMoHuoIJ) I got the impression that we probably shouldn't allow removeExisting for non-referenceable nodes. However, the alternative (remove and replace the existing node) is equally arguable.