This reminds me once more of a piece of the puzzle which we're still missing. Markdown + git is great, but leaving your blog up on Github is just another central point of failure; Github feels like a fact of nature right now, but it's just a website at end of day.
Most broadly, it's called content-centric networking. Bittorrent is a piece of that puzzle, but too static, with no obvious way to connect disparate hashes together into a single entity. IPFS and Secure Scuttlebutt are groping in the right direction.
There was a project called gittorrent which, as you might guess, was trying to be 'bittorrent for git'. It never really went anywhere, the crew at https://radicle.xyz are looking to revive it and I wish them the best of luck.
What I want is a single handle, such that, if there are still copies of the data I'm looking for, out there on the network, I can retrieve them with that handle. And also, any forks, extensions, and so on, of that root data, with some tools to try and reconcile them, even though that may not always be possible.
That would be really powerful. It would made information more durable and resilient, and has the potential to change the way we interact with it. Like I find typos in documents sometimes, it would be nice to be able to generate a patch, sign it so it has a provenance, and release it out into the world.
When I browse old blogs which still exist, I routinely hit links to other blogs, video, and the like, which are just gone. Sometimes Wayback Machine helps, often it doesn't. This problem can't be fixed completely, when data is gone, it's gone, but we could do a lot more to mitigate it than what we're doing now.