Re: setNamedItemNS(namespaceURI, localName)

It looks like someone is confusing this setter method
                   Node setNamedItemNS(in Node arg)
raises(DOMException);
with its corresponding getter:
       Node getNamedItemNS(in DOMString namespaceURI,  in DOMString
localName);

Note that the arguments are different. In the setter, we're inserting a
particular Node, and using that node's  name  -- which is a two-part value
made up of its localname and its namespaceURI, as stored in the node
itself. In the getter, we're specifying that two-part name and expect the
matching node (if any) to be returned.