Content system patterns repository [on hold]

Does a pattern library for content systems exist?

I think that content systems for group interaction like wikis, forums (Reddit-styled or traditional), message feeds, chats (Slack), blogs, link directories (Yahoo/DMOZ), and Q&A's (like StackExchange) are not fundamentally different from each other.

They can be modelled as composed of shared "classes" of objects (post, comments, likes, etc.) with various relationships connecting them.