So i’ve tried a few things and I think I have located the problem.
The comment topics are created properly in Discourse and they have the following url :
http://discourse.domain.net/t/name_of_blog_post/14/1
But I checked what url the embed part was looking for and Firefox gave me this
http://discourse.domain.net/embed/comments?embed_url=%2Fname_of_blog_post%2F
Why does that difference exist ?