For a workaround for now, you can just make a span with onclick, etc.
bugzilla = s|((?:bug|b=|(?=#?\d{4,}))(?:\s*#?)(\d+))|<span
style="text-decoration: underline;" onclick="event.preventDefault();
document.location = 'https://bugzilla.mozilla.org/show_bug.cgi?id=\2';"
onmouseover="window.status = 'https://bugzilla.mozilla.org/show_bug.cgi?id=\2';"
onmouseout="window.status = '';" title="View bug \2">\1</span>|i |