It looks like there is something bigger going on.
The headers X-Frame-Options are set to ALLOWALL.
But but ALLOWALL is not an option see X-Frame-Options - HTTP | MDN
If I try to embed the comments I get the next error: An invalid X-Frame-Options header was found when loading ... 'ALLOWALL' is not a valid guideline
Only when I use topicId the comments load. But I think this is because you dont need the full permission when you just embed the comments.