Thanks for the addendum. :-)
Mingli Yuan, 01/07/2014 08:44:
The content provider label their own content with some metadata. And Twitter/Facebook/etc will show a rich content on their timelines.
https://bugzilla.wikimedia.org/showdependencytree.cgi?id=54829&hide_reso... tracks this. Bug 30113 has a small patch attached, if you want to give a look.
Nemo