Certain elements though inside, reappear outside upon reading, setting, deleting, outerHTML.
e.g. (recent case study)
<?xml:namespace prefix...> (e.g. original source was rtf) deep inside one <p></p> appears upon readup of any other <p>; (Also <?xml has no closure to prevent this).
e.g. (furthermore; codewrecker)
Replacement of said-same by <p> corrupts the all.tags("P") collection, stuffing-in <?xml, such that the next-item is element.outerHTML=="<?xml..." but element.tagName=="P"!