Fix disqus avatar-hover issue.
Fix disqus avatar-hover issue.

In disqus-powered sites, hovering over an avatar pops an
info card on the poster, and also incidentally removes
and re-adds the comment node. It turns out that the
MutationObserver already watching for new comments can
handle this case, but needed an xpath tweak to account
for comment nodes being removed/added directly, instead
of their parent <li> node being added/removed.

fizbin/killfile-extension,fizbin/killfile-extension