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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
I tried to implement some linting rules for quotation mark and punctuation once. Took me way too much time and effort. It's mostly trial and error but good enough I guess to highlight the most blatant abuses.
Anyway, here is the code: https://github.com/sindresorhus/awesome-lint/pull/101/files
Multi-line strings in JSON are also an embarrassment: https://stackoverflow.com/a/2392888
As a consequence, the amount of parsing and processing that you need to do is really bad for performance. Of course, there are formats like YAML and TOML that go in the opposite direction - they try to cover all use cases and end up being overcomplicated.
There are occasionally other attempts like JSON5 to improve things: https://json5.org/
However those also oftentimes are not very popular, because there is just too much ecosystem that has been built around the older formats, like XML, JSON and even YAML.