Help: how to display HTTP comments on HTTPS version of page?

The Facebook Comments Box social plugin accepts an href parameter specifying the URL related to the content.

The page includes a <meta property="og:url"> element to collapse multiple references to the same content down to a single URL reference; /foo and /foo?source=email both contain an og:url of /foo and therefore map to the same object.

The Facebook plugin for WordPress passes the get_permalink() value returned by WordPress through the facebook_rel_canonical filter to be added as an href parameter in the social plugin markup as well as the og:url of the page.
https://github.com/facebook/wordpress/blob/master/social-plugins/class-facebook-comments.php#L460

Thanks for the reply! We actually worked it out ourselves just yesterday and published this blog post explaining it in case others might benefit:
https://www.mightyminnow.com/2014/05/how-to-make-social-media-shares-counts-and-comments-work-across-http-and-https/

Glad to have our suspicions confirmed!