What sort of inclusions in the news do you mean? Images, links etc?
inclusion from a different, foreign source with no control for the content
any examples: if you write your own news, you know, its not possible, to build malformed content, if you use only the editor in news to add the content, but if you copy that news from a third party webpage, its possible, that this webpage use malformed content
other example: a wrapper inside of a iframe in connection with one of the conditions in filterCSStoHead.php
if the filter works, he try to move a <link> or a <style> inside of the defined areas to the correct place between <head> and </head>. if the output content use a double <body> or double <head>, its not possible, to found the correct start point