Markdown really should have more widespread support than it does. It’s just the right mix between plain text and an office document, I took my college notes with it in fact cause of how fast it was to format stuff. But as far as I know, there’s no default program on any of the (major) OS’s or Distros for viewing it.
Maybe it’s just due to a lack of standards for formatting or something, but regardless I do wish it was used and supported more.