It seems to be more complicated. These comments are in reply to a post on Minds, but they aren't shown.
https://gleasonator.com/@hindudindu@www.minds.com/posts/AZJuBhO0BLGfmgPh9E
Discussion
I agree. I was also experiencing some bugs like that.
My understanding is that their database has "posts" and "comments" in a separate table, more like Facebook rather than Twitter. They had to work around that to implement ActivityPub, figuring out which messages would be considered "posts" and which "replies", and then putting them through the proper pipeline to convert them into one or the other on their end. That would be complicated.