A kbin user has the most upvoted comment chain on that post.
https://kbin.social/m/meta%40lemm.ee/t/458933/How-do-I-block-all-of-Hexbear-from-All/top
sh.itjust.works and a 1-user Lemmy instance called lemmy.magnor.ovh also see and reply to Hexbear comments, though Hexbear doesn’t see their replies:
I know it’s really really really funny but seriously, why is this even a thing? Federation has such a half-assed implementation.
Hexbear’s posting energy is so strong it breaks containment.
Because of not conforming to the protocol, which can hardly be blamed on lemmy.