I produced these nodes basically by bypassing the complete webserver and directly running the code that creates the XML. That XML is produced by (a hacked version of) XML::Fling - I don't know how it handles well-formedness and how it relates to "real" XML.

Update: Hmmm - I just noticed - XML::Fling does not exist on CPAN, so likely it was written by one of us... Anyway - I guess it only encodes the characters necessary to ensure proper XML-escaping, that is, anything matching /[<>&]/.