One last comment regarding this issue. You can't use a namespace in
RSS without adding a declaration for the namespace, like so:

<rss version="2.0"
xmlns:dc="http://purl.org/dc/elements/1.1/">
</rss>

The XML in Namespaces specification calls this declaration an attribute:

http://www.w3.org/TR/REC-xml-names/#ns-decl

"A namespace (or more precisely, a namespace binding) is declared
using a family of reserved attributes. Such an attribute's name must
either be xmlns or begin xmlns:. These attributes, like any other XML
attributes, may be provided directly or by default."

So if RSS forbids namespace attributes to core elements, doesn't that
forbid namespace declarations in the RSS element?