OK guys ... I managed to resolve here after a lot of fighting, the flow is as follows:
1- Create your facebook app with any name; 2 - configure the same to be an app of a website and make the same public; 3- In the app's platform configuration, select 'site'; 4- insert the
<meta property="fb:app_id" content="(seu app id)">
before the head closes; 5 - enter jdk shortly after opening:
<div id="fb-root"></div>
<script>(function(d, s, id) {
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)) return;
js = d.createElement(s); js.id = id;
js.src = "//connect.facebook.net/pt_BR/sdk.js#xfbml=1&version=v2.10&appId=(seu app id)";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>
6- Insert the tag in the location where you want the comment box to appear:
7- Go to the comment moderation setting, click Settings, and enable 'comments mirroring' or 'comments mirroring', something like this. link
At this point the comments should already be appearing with 'mirroring'.
Any questions may ask me. hug.