I feel a little sad that pay-walled articles make it to the top of HN. I'm sure the article is interesting, but a lot of us can't actually read it.
javascript:window.location.href='https://m.facebook.com/l.php?u='+encodeURIComponent(window.location.href);I didn't come up with this trick, but unfortunately I forgot who donated it.
It seems likely that they know about this backdoor and have opted to allow it. They must surely know the IO addresses associated with archive.is and have yet to make any effort to block then.