As an extension to my note on media-native programming languages, I wanted to note: Oak's standard library contains built-in support for not only parsing and rendering JSON, but also Markdown content via the
md libraries. Markdown support is built into the language tooling, and it means when I write Oak programs, I feel like Oak "speaks Markdown" natively as an information format. It means there's no additional development effort for Oak programs to really support Markdown -- supporting it is about as easy as supporting plain text, at least in rendering, processing, and parsing. As a result, most tools I'm building with Oak where Markdown support makes sense, like this stream site, support Markdown.
I think this demonstrates one successful case study of a language that built in support for unconventional data formats, and benefited in the kinds of software and tools built from it.