The notes aren’t stored inside the app. They’re plain files on disk that the app happens to display — which means the app can disappear and the notes don’t.
Most note-taking and knowledge-base tools store your data on their own servers, in their own proprietary format — convenient while the company exists, but your notes are only as durable as their business model. Obsidian’s design commits to the opposite trade: every note is an ordinary markdown text file, sitting in an ordinary folder, readable by any text editor with or without Obsidian installed. This is what researchers call “local-first software” — an approach that treats offline availability, longevity, and user ownership of data as first-class design requirements rather than an afterthought layered on top of a cloud service.
That’s the property this essay is actually leaning on when it describes “an Obsidian vault with multiple levels of knowledge systems baked in one place” — not a specific feature of the app, but the fact that a personal knowledge base built this way survives independently of whichever software is reading it this year.
Source: Kleppmann, M., Wiggins, A., van Hardenberg, P. & McGranaghan, M. (2019), “Local-first software: you own your data, in spite of the cloud,” Proceedings of the 2019 ACM SIGPLAN International Symposium on New Ideas, New Paradigms, and Reflections on Programming and Software (Onward!), 154–178.