I think a great use case for this is for working with files locally. I had to change the script tag to use a relative link, but then it opens up fine as a local file. Now I can share those files via DropBox or the like, so it's very end-user friendly.
If you were writing a desktop application, you could be saving user data as this JSON-HTML quine (JHQ?), so it's automatically accessible on any device, but also still accessible to e.g. the jq utility.
Since any modification is liable to move the "_" field, you might address that by using an array envelope instead; [{"real": "data"}, "<html><footer>"]
For a production site, I think you ought to, server-side, check the Accept header and pre-render the conversion.
Another note: if I do Save Page As in Firefox, it saves the page as standard HTML, losing the JSON.
If you were writing a desktop application, you could be saving user data as this JSON-HTML quine (JHQ?), so it's automatically accessible on any device, but also still accessible to e.g. the jq utility.
Since any modification is liable to move the "_" field, you might address that by using an array envelope instead; [{"real": "data"}, "<html><footer>"]
For a production site, I think you ought to, server-side, check the Accept header and pre-render the conversion.
Another note: if I do Save Page As in Firefox, it saves the page as standard HTML, losing the JSON.