Last modified: 2013-06-24 02:07:19 UTC
They get stripped out when rendered back to HTML. e.g. <ref>Foo<!--bar--></ref> -> <ref>Foo</ref>
Related URL: https://gerrit.wikimedia.org/r/70060 (Gerrit Change I3bbea49132ef4a720a147ba9b170c39a0c00f711)