There are a couple I have in mind. Like many techies, I am a huge fan of RSS for content distribution and XMPP for federated communication.
The really niche one I like is S-expressions as a data format and configuration in place of json, yaml, toml, etc.
I am a big fan of Plaintext formats, although I wish markdown had a few more features like tables.
No, in general the markdown format suggests using line breaks in the middle of paragraphs to make the code just as readable as the output. That’s why two line breaks is what creates a new paragraph. So it’s the viewer showing it incorrectly here.
The screenshot is of the website ietf.org , which doesn’t seem to be markdown.