In the top days of Bubblews, three years ago, you bumped into a Google recaptcha like barrier when you posted links on Facebook. With a title that posting from site this-and-this is unwise and could be harmful. Too bad I didn't make some screenshots of this shameless activity.

Here is an article about blocking Tsu:
https://www.wired.com/2015/11/facebook-banning-tsu-rival-social-network/

Looks like that the methods are a bit more subtle these days :)