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5.1 Element-Level Namespaces says that the only namespace declarations used should be on <html> <svg> and <math> but the xhtml namespace must be declared on any html elements used as children of svg or mathml elements. so <math xmlns=".....">.....<mtext>...<b xmlns="http..xhtml">zzz</b>...</mtext>... otherwise the html parser will put the <b> in the xhtml namespace (and it will work) and the xml parser will put <b> in the mathml namespace (and it won't work)
Section 5.1 has been rewritten to include this paragraph: Polyglot markup declares the default namespaces on the root HTML element <html>, the root SVG element <svg>, and the root MathML element <math>, and on any HTML elements used as children of SVG or MathML elements. Polyglot markup does not declare any other default or prefixed element namespace, because [HTML5] does not natively support the declaring of any other default or prefixed element namespace. I believe that this satisfies the request of this bug. Thanks for you continued feedback. Eliot
mass-move component to LC1