alt Hacker NewsPlain text is great as far as it goes, but when it comes to structure you start from zero for every file. There’s always someone getting wistful about ad-hoc combinations of venerable Unix tools to process “plain text”, and that’s fine when you’re in an ad-hoc situation, but it’s no substitute for a well-specified format.
XML, JSON, YAML, RDF, EDN, LaTeX, OrgMode, Markdown... Plenty of plaintext, but structured information formats that are "yes, and". Yes, I can process them as lines of plain text, and I can do structured data transformations on them too, and there are clients (or readers) that know how to render them in WYSIWYG style.