Interesting, wonder if it's a number of articles restriction or similar, you might try just dumping your cookies, trying private browsing mode or setting Privacy Badger or similar to eat them for that site.

You could also try the Facebook linkout method:

http://facebook.com/l.php?u=<URL> (or just otherwise spoof your referrer to facebook.com)

Yet to find a paywall willing to deny social media traffic. They'll die without it and they know it.