Markdown comments

[John Gruber]

The other side of the coin is that Markdown is not an XML nanny.
There's an assumption with Markdown's handing of inline HTML tags
that it is up to you, the author, to use raw HTML in a well-formed
way.

Markdown's raw HTML support is garbage-in, garbage-out.

I think this tenet has served Markdown well, and if we apply this
logic to comments, I think one could make the argument that the
rule should be "Use XML commenting rules" and leave it up to the
author not to include "--" if they care about XML compatibility.

Flipping back once again to the other side of the coin, though, I
would argue that very few people are aware of these issues about
"--" sequences in SGML, HTML, and XML commenting rules. Even
people who know the basics of HTML, and who feel comfortable
inserting raw HTML tags into their Markdown documents, might have
no idea that a comment like this is invalid:

    <!-- This -- or that -->

-J.G.