Whether from the file system or the markdown structure or the block hierarchy, the base structure of notes should be nested lists. Everything should be a list, and the depth of markdown headers should be ignored. The top level header of the exported content is the h1.
Discussion
Notes are books. Reading and writing notes are very close to each other. Software should make it easy to bring in, and read, the public notes of others. A wiki is nothing more than a group of people's notes. Imagine a map of personal notes linked to the knowledge of the world.