They either warn or block all urls:

warning: https://www.facebook.com/l.php?u=https://afsdfsfsfsdfsddsddd...

blocked: https://www.facebook.com/l.php?u=https://facebook2.com

It's just a standard notice, warning you that you're leaving Facebook and going to an external page. Most likely to prevent phishing.

Did you create that link manually or did somebody actually try to share Facebook through Facebook?

Priceless. This shows that generic messages can convey bad messages.