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That's a little too far in the machine direction, it would be annoying for humans to read.

Yaml then?

Yaml I think would take too much vertical space and make reading the normal thread not as useful as it is right now.

Yeah, the balance has to be between ease of reading and ease of typing into the browser's plaintext input box. It just has to be easier to parse than what is now...which, to be honest, isn't terribly hard to parse, but it's enough of a barrier to make it more than an afternoon hack project.

If you're going to use JSON, why not make the format compatible with schema.org JobPosting (http://schema.org/JobPosting) with JSON-LD?

Job Description Markup Language (JDML) is an industry standard with great Java support. Why reinvent the wheel with a custom JSON format?

LOL, I don't think it does what you are thinking it does: https://workspace.imperial.ac.uk/lesc/Public/jdml.pdf

Also, your post is right now somewhere around #6 on google for "Job Description Markup Language".