Yesterday I found Interstellar which has this feature. I assume mainly because it is not only a Lemmy app, but also a PieFed one, which has this feature in the reference frontend (AFAIK).
Are there other Lemmy apps or frontends that support thread merging?
When the same link is posted multiple times, the comment sections from each community it’s posted to are all displayed on one page.
It’s like merging multiple communities together against their knowledge, will, or consent, because people are too fucking lazy to use the Subscriber feed.