Last modified: 2011-03-13 18:05:02 UTC
See the url. The header where change, but the old red text is not inside the h-tag. That is wrong, because the header where changed, so the old and new text has to shown inside the header. The old text is already wraped into a span with class="mw-headline", but is not inside of the h-tag.
HtmlDiff is removed from core (bug 19859)