Of course it's extensible, you can put HTML in it, and HTML is extensible.

That is like saying "Ruby is not slow, you can write native extensions in C". No, Markdown is not extensible.

	▲	tlarkworthy a day ago \| parent [-]
		Ruby is extensible as well, these things flourish because their creators thought hard about escape hatches. The things that are not extensible we don't talk about because they already died.