While not anything blockchain-based, I had a similar thought of just doing social media through a single text file that you can add to/remove from whenever, and re-post the whole thing[0]. Literally HTTP POST it.

Edit, amend, add, delete, schedule, etc., all from a single text file. I haven't worked on it in a few weeks but I intend to get back to it soon.

[0] https://post.mw