@claus@fosstodon.org that's funny that you got two different answers from @sl007@digitalcourage.social and @nik@toot.teckids.org

They're both right.

Seb means Server A sends the reply to Server B (who then shows it to User B, who isn't in your example but I trust you know who I mean 😉 )

Nik means server B is doing the final delivery by showing user B the reply (I think that's what he meant.)

Server B is only aware of any replies that are sent to it, so server A must be doing the delivery.