Ecamm will only receive comments from Facebook when a stream to your Profile is Public. Streams to Only Me and Friends Only will not receive comments.
If you are streaming using the Public setting above, and still not receiving comments in Ecamm, ensure that the broadcast is actually Public by checking the post's privacy status on your Facebook profile page for the globe icon:
If the post is showing up as Friends Only or Only Me even after setting Ecamm's Post to menu to Timeline (Public), this indicates that you need to change Ecamm's posting permissions using the steps here.