I'm not Japanese (forgive me if this comes across as appropriation).
From what I've seen, if you browse through Japanese feed, you'll rarely see replies/threads- actual replies are posted as new notes without tagging original post. I've come to understand it's how they use SNS - it seems more like a collective stream of consciousness.
I'll be grateful if it's possible to remove mattn-san from spam but understand if you don't want to start making exceptions.
(I'll also try requesting mattn-san to delete the posts but not sure he'll see my note)