Yeaahhhh I don’t know about that… likely all instances are processors. And the on he subscribe to would be controller. Somewhat because to my knowledge no one really decides of particular treatment of the user data (it’s all rather communist architecturally). So maybe every instance would be join controller…
And in the end up to the (join) controller to cascade the request. That’s part of why it’s a thing of beauty to watch it happen on the feddiverse 😅