One of the principles behind the design of fn:deep-equal() was that a node
should always be deep-equal to itself (that's why we defined NaN = NaN, for
example).

But as currently written, the rule for comparing namespace nodes (or
"bindings") requires (node-name($i1) eq node-name($i2)), which will not be true
for an unnamed namespace node (the default namespace), because node-name()
returns () for such a node, and (() eq ()) is ().

This doesn't affect XQuery 1.0 because namespace nodes are inaccessible, but it
does affect XPath and XSLT.