[lisper]

> The original use case for markup is that you can take a piece of plain text and then mark it up with tags

Yes, that was the original use case, but in actual practice HTML has not been used that way for a long time. Nowadays HTML is de facto used as a programming language for the visual representation layer of a browser. No one actually uses HTML to mark up documents by hand any more, for two reasons: first, no one writes plain text documents to use as source material for markup. They write Word documents, or TeX documents, but plain text source is all but unheard of nowadays. And second, HTML syntax is too clumsy and places too many demands on the user. So when ordinary people want to produce HTML they use WYSIWYG editors. When geeks want to produce HTML (and remember I'm talking about documents here) they use markdown. The only time anyone writes HTML nowadays is when they want to make a browser do something fancy.