I guess you could do syncing kind of like how CCing email is done. CC my home server and global server. This gives you agency to remain detached from the hivemind, and vice versa. This is not some idea out of left field, it's roughly my workflow between Reddit or HN or other sites. I manually do the filtering in my mind when I move through different channels.

Phpbb is open source, but I mostly brought it up to show that Facebook is just that, and nothing more. Forking Reddit will also give you a Facebook clone (and a Reddit clone).