This person's criticism is silly. Markdown documents are extensible: the entire point is that it makes the main parts require less cognitive load, and allows you to use HTML for the rest.
## CHAPTER IV.
#The <white>Rabbit</white> Sends in a Little Bill
It was the <white>White Rabbit</white>, trotting slowly back again, and looking anxiously about as it went, as if it had lost something; and she heard it muttering to itself *“<red>The Duchess</red>! <red>The Duchess</red>! Oh my dear paws! Oh my fur and whiskers! She’ll get me executed, as sure as ferrets are ferrets! Where can I have dropped them, I wonder?”* <gold>Alice</gold> guessed in a moment that it was looking for the fan and the pair of white kid gloves, and she very good-naturedly began hunting about for them, but they were nowhere to be seen—everything seemed to have changed since her swim in the pool, and the great hall, with the glass table and the little door, had vanished completely.
Just write the two lines of CSS required for those elements, and bam! You're all good!
They criticize this within, but their criticism isn't particularly strong: sure, the point of Markdown is to write less HTML, but in this instance, the HTML is about as semantically concise as you can get: the quickest solution in any system. Their comment on hybrid documents also doesn't really work in the context of most parsers.
It emerged at the time when HTML was the lingua franca of the Web. Nowadays with so many new ways to create web pages you can't count on it, so contributors who aren't familiar with it will spend unnecessary time on fixing HTML and CSS instead of fixing the docs.
A div isn't the right thing to use here. Am I missing the point of your example? It seems like it could be a way to demonstrate how people don't know HTML, but I'm not sure.
They criticize this within, but their criticism isn't particularly strong: sure, the point of Markdown is to write less HTML, but in this instance, the HTML is about as semantically concise as you can get: the quickest solution in any system. Their comment on hybrid documents also doesn't really work in the context of most parsers.