If you take content discovery out of the protocol, I would say it then behooves you to put at least an example of content discovery into the reference implementation.
There's a big difference between creating a protocol that's intended for fully-content-agnostic communication over the Internet (eg, HTTP) and creating a protocol that's specifically intended to be used to build a social network. The latter type needs various features that enable the type of behavior we know people on social networks desire from them. It does not, as you say, necessarily need to encode strong opinions about how content discovery should be done into the protocol at a fundamental level, but it at least needs to acknowledge that that is a thing that will be necessary for any social network to succeed.
There's a big difference between creating a protocol that's intended for fully-content-agnostic communication over the Internet (eg, HTTP) and creating a protocol that's specifically intended to be used to build a social network. The latter type needs various features that enable the type of behavior we know people on social networks desire from them. It does not, as you say, necessarily need to encode strong opinions about how content discovery should be done into the protocol at a fundamental level, but it at least needs to acknowledge that that is a thing that will be necessary for any social network to succeed.