Great article! Definitely one of the cool underused URI schemes (like tag: ‒ a suggestion for the next #spec-of-the-week 😉). For implementation and use in action, check out https://github.com/IS4Code/SFI ‒ it uses ni: URIs to identify pieces of data (with ?ct too, as a counterpart to data:) and stores metadata about their contents. Then you can use something like https://archive.data.is4.site/.well-known/ni/mh/4ucCCA1uFg5qaoIm to store and provide the metadata through an RDF triple store, which is very cool!