This incident has been resolved.

Facebook deployed the fix and the issue seem to be mitigated now. This has also been reflected on Facebook's status page: https://developers.facebook.com/status/issues/353480721999225. We'll continue monitoring to ensure the issue is fully resolved.

Our automated systems have detected that we stopped receiving events for Page Feeds from Facebook which is impacting Acquire Users from Comments functionality. The problem has been reported and Facebook Team is working on it. You can check progress in the bug tracker here: https://developers.facebook.com/support/bugs/2102574809869104 and https://developers.facebook.com/support/bugs/642531419852977.