Not sure I follow. You're not going to suddenly discover after two days of writing that you need a top-level header for the whole document, but you might very w

Not sure I follow. You're not going to suddenly discover after two days of writing that you need a top-level header for the whole document, but you might very well discover that one of your "leaf" sections needs to be broken up further. The difference being that in your scheme I'd need to change all existing headings in the document to handle that. Another (minor) thought: if you're the type who starts by outlining the whole doc with headers only, the Markdown approach naturally makes indentation follow structure.