"The whole point of ActivityPub as an open protocol is to turn Twitter/Instagram-like social networking into something more akin to email: truly open."
The point of an open protocol is to help folks build what they want to build. Not an obligation to welcome everyone into their house.
If I have a full beer keg and you have a tap that fits it, that doesn't necessarily mean you're invited to my barbecue.
@lmorchard Point of order, open like email where the small players have deliverability issues to the big providers and the anti-spam arms war spirals up (in price) with every year?