Yes, I should have been clearer. Reddit and Instagram do not operate this way today, but open social alternatives to them could. The idea is that people create personal websites where posting, commenting, and other social actions live, and that becomes the filesystem they own.

Open social networks would simply index or pull from those sites using agreed-upon lexicons and protocols. Existing platforms could either adopt the open social model, or, more realistically in the short term, be treated as syndication targets where posts are pushed via their APIs when someone publishes on their own site.