Comment by rexxars

For a real-world use case: Sanity used this trick[0] to encode Content Source Maps[1] into the actual text served on a webpage when it is in "preview mode". This allows an editor to easily trace some piece of content back to a potentially deep content structure just by clicking on the text/content in question.

It has it's drawbacks/limitations - eg you want to prevent adding it for things that needs to be parsed/used verbatim, like date/timestamps, urls, "ids" etc - but it's still a pretty fun trick.

[0] https://www.sanity.io/docs/stega

[1] https://github.com/sanity-io/content-source-maps