Not the thread, not the user page. Nowhere. Just gone. I do also have the case where it disappears but a refresh / going to the user page will show it, i.e. so

Not the thread, not the user page. Nowhere. Just gone. I do also have the case where it disappears but a refresh / going to the user page will show it, i.e. something async on their end was just a few milliseconds too slow or something. And posting the exact same comment again (I c+p them now) works. So it wouldn't be any automatic removals and it's too fast for manual removals.