A paragraph is one type of item in a Story written in the simplest and most preferred markup consisting of just words and links.
Items marked up in HTML or Markdown are not paragraphs in the technical sense. We sometimes refer to them as "paragraph like items" glossing over this distinction.
Paragraphs markup Internal Links as a title inside double square brackets.
Paragraphs markup External Links as a URL and link word inside single square brackets.
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And here we come to something that is very hard to get about Federated Wiki which Mike Caulfield would love your help explaining — Ward likes to say his interest is can you take a few simple ideas and data structures and make them really generative. And so you have this simple idea of paragraphs as the atomic structure rather than pages, and suddenly the lousy revision histories we have turn into this beautiful, almost poetic view.