Recently, I’ve noticed federated threads/comments/votes were lagging behind, and it turns out kbin.earth was being spammed (hundreds in a minute, leading to a couple thousand queued messages after only half an hour) by a Lemmy server with the same exact activity pub message. After blocking the server (feddit.de), federation should now work correctly. If the admins of the server ever fix the issue, I’ll be glad to unblock it.