fidelio I don't really understand why you'd use Facebook comments that way on Flarum... but here's how you could achieve something like you show on your screenshot:
You'll need to extend the CommentPost
javascript component to add content underneath.
The signature extension might be an example https://github.com/Extum/signature/blob/master/js/forum/src/main.js#L20 . It's not compatible with beta 8/9/10 itself, but the code that inserts new items below the content is still relevant.
You'll probably also need to check if this.props.post.number()
is 1
to only append to the first post, and maybe you'll need to get the post or discussion ID to pass along in the Facebook integration code.
Depending if the Facebook is an iframe or a javascript library, the exact way to embed their HTML might vary. If it's an iframe, it can simply be added via a Mithril dom helper (m('iframe', {src: 'yoursrc'}
) but if it's a javascript lib like they do for the posts embed, then you'll need to do something similar to the ReCaptcha extension to load the javascript first.