btw, what were you expecting when/if Some Enormous Fucking Website exposes an ActivityPub endpoint for their past 10-20 years of post data (YouTube, maybe) and the comments are replies to the video that **don't have mentions of the video author's username**? Or simply, all the posts don't have mentions for every user involved in the thread because that's Twitter behavior that started from Twitter and only makes sense on Twitter and Twitter clones?