I think we need to think of social protocols less as a technical solution and more as what I'd describe in my day job as a 'business process'. Sure, part of this will be tech-enabled and parts will be fully automated, but I feel that what is really lacking is an internet etiquette that can be abstracted over different channels or platforms.

Consider Facebook. With the friend request it invented a new social protocol. It was based on an underlying technical need (this platform will allow you to message, interact with and view the content of this target user) but became a social contract (I assert that I know and am willing to interact with this person on a level where they can see my daily updates and information that I have chosen to share). This was incredibly rigid and binary, but essentially shaped the social media landscape and affected the way that users, especially early users considered their friendships and acquaintances.

Also its a bit out of vogue now, but there was a massive 'thing' of the facebook relationship status being some kind of social registry.

If anyone has read the 'Kingkiller' chronicle books by Patrick Rothfuss, I would imagine a 'social protocol' to be something like the 'rings' system from the city of Severin. Simple ruleset, but allows complex social emergent behaviour and could be abstracted over different mediums or communications channels.