User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)
Since this information isn't otherwise readily serializable (as it would be adding namespaced attributes or the like), it's convenient to be able to trigger these user data handlers.
Created attachment 430516 [details]
Demonstrates lack of NODE_DELETED support and workaround but only for some non-Mozilla browsers
I believe the decision on NODE_DELETED is that we have no plans to implement it.
Yeah, the problem is that it's too hard to implement interoperably due to being too dependent on GC behavior.
Right, see bug 324871, comment 17.