Broken Anchor Links on Handbook Pages

In the markdown of /handbook/security/, I'm seeing a line under each header like {: #my-anchor-text}.

However, it doesn't seem to be adding anything to the rendered HTML, so links within the doc to #my-anchor-text do nothing. But our Kramdown blog post seems to say that {: #custom-id } should work.

Per @marcia: "I think the new anchors on hover may be causing the JS to override kramdown’s custom ID" - so we need to further investigate and make both types work or maybe replace the bad, 'manual' anchor links.