Semantics. Notions of tags, replies, metadata, what kind of entity a link is refering to. Stable identifiers (how do you canonically refer to content rehosted e

Semantics. Notions of tags, replies, metadata, what kind of entity a link is refering to. Stable identifiers (how do you canonically refer to content rehosted elsewhere?). Authenticity for rehosted content. There was/is an idea and attempt at "semantic web" aka "web 3.0" but it never caught on. https://en.wikipedia.org/wiki/Semantic_Web https://en.wikipedia.org/wiki/Semantic_Web Also, a common requirement is authenticated reads and fine-grained access control of pull-based content. E.g. I want to share my vacation photos with a different subset of friends/followers vs my tech blogging, only some of which should be public.