When sending torrent links (Ubuntu / Arch iso even), FB blocks it. Usually they show a red exclamation point on the message for me so this is quite weird. Of course, this is one of the reasons I don't use FB anymore.
This one also shows a red exclamation point, but because of a bug the exclamation point goes away after you send more messages. You can see it in the twitter screenshots or replicate yourself by sending any gnews link on messenger
