Markdown and footnotes: most natural format missing?

Question

Markdown and footnotes so far

I'm referring to Markdown: Syntax at daringfireball.net, which seems to be primary source for Markdown syntax.

Markdown is known to be based on already existing formatting in mails and newsgroups. In mails and newsgroup, I often see something like this for footnote and forwarded references:

Blah, blah [1] blah, blah.

[1] http://somesite.com/somepage.html#someanchor

Surprisingly, this very common format, is not part of the primary Markdown reference. It only knows something like:

Blah, blah [some title][id] blah, blah.

[id]: http://somesite.com/somepage.html#someanchor

And I have never seen any using this spontaneously in either a newsgroup or a mailing list, while the former is very common.

I could just find something called PHP Markdown Extra, which has something closer to the common spontaneous usage, while different enough:

Blah, blah [^id] blah, blah.

[id]: http://somesite.com/somepage.html#someanchor

Closer, but I still never seen anyone using this in a newsgroup or mail.

The question

I wonder why a so much common usage is not part of the primary markdown reference, and even not part of any variant I know. If someone knows some reason for this, I'm interested in knowing this reason. On the other hand, if I just missed something, like missing a markdown variant which is of very common use and includes the in practice most natural way of writing a footnote or forwarded reference (the first one introduced in this post), then I would like to know it.

Answer 1

...why a so much common usage is not part of the primary markdown reference, and even not part of any variant I know.

It looks like some of it is available per How do I format my posts using Markdown or HTML?:

Links

Here's an inline link to [Google](http://www.google.com/). Here's a
reference-style link to [Google][1]. Here's a very readable link to
[Yahoo!][yahoo].

  [1]: http://www.google.com
  [yahoo]: http://www.yahoo.com/

Advanced Links

Links can have a title attribute, which will show up on hover. Title attributes can also be added; they are helpful if the link itself is not descriptive enough to tell users where they're going.

Here's a [poorly-named link](http://www.google.com/ "Google").
Never write "[click here][^2]".
Visit [us][web].

  [^2]: http://www.w3.org/QA/Tips/noClickHere
        (Advice against the phrase "click here")
  [web]: http://programmers.stackexchange.com/ "Programmers Stack Exchange"

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Also see Markdown footnotes? at Meta. The page mentions Markdown With Footnotes.