2.2.49 [W3C-HTML51] Section 9.3 Serializing XHTML fragments

C0083: When XHTML documents are serialized, prefixes and namespace declarations are adjusted as needed

The specification states:

 9.3 Serializing XHTML fragments
     ...
     In both cases, the string returned must be XML namespace-well-formed and must be an 
     isomorphic serialization of all of that node's relevant child nodes, in tree order. 
     User agents may adjust prefixes and namespace declarations in the serialization (and 
     indeed might be forced to do so in some cases to obtain namespace-well-formed XML). 
     User agents may use a combination of regular text and character references to 
     represent Text nodes in the DOM.

EdgeHTML Mode

When XHTML documents are serialized, prefixes and namespace declarations are adjusted as needed.