From the webpage:
Markdeep is a technology for writing plain text documents that will look good in any web browser. It supports diagrams, common styling conventions, and equations as extensions of Markdown syntax.
Markdown is free and easy to use. It doesn’t need a plugin, or Internet connection. There’s nothing to install. Just start writing in Vi, Nodepad, Emacs, Visual Studio, Atom, or another editor! You don’t have to export, compile, or otherwise process your document. Here’s an example of a text editor and a browser viewing the same file simultaneously:
Markdeep is ideal for design documents, specifications, README files, code documentation, lab reports, and technical web pages. Because the source is plain text, Markdeep works well with software development toolchains.
Markdeep was created by Morgan McGuire at Casual Effects with inspiration from John Gruber’s Markdown. The current 0.01 beta release is minified-only to find bugs and get feedback, but a full source version is coming soon after some more code cleanup.
You may find this useful but I certainly disagree with writing “design documents, specifications, …., code documentation, lab reports, and technical web pages” in plain text.
Yes, that fits into software development toolchains but the more relevant question is why haven’t software development toolchains upgraded to use XML? Unadorned plain text is better than no documentation at all but the lack of structure makes it difficult to stitch your documentation together with other documentation.
Unless preventing transclusion of documents is a goal of your documentation process?
The XML world has made a poor showing of transclusion over the years. That was driven by the impoverished view that documents are the proper targets of URLs and not more granular targets within documents.
That “document as the target” view perpetuated an eternal cycle of every reader having to navigate the same document to find the same snippet that is of importance.
Perhaps XQuery can free us from that eternal cycle of repetition and waste.
A meaningful and explicit structure to documents is a step towards XQuery accomplishing just that.