@AltCode That's a good question. At this time I can only try to provide as much linkage and context as I can, and it's up to individual implementors to handle.
In #nodebb's case, each post will have an inReplyTo that points to its direct reply. OP (the root level post) does not have an inReplyTo.
All posts send audience which points to the TOPIC. Each topic (the Page object) sends audience which points to the category.
#FEP 1b12 leaves no room for topic references in replies 🫤