Markdown and footnotes: most natural format missing?
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.
Have a nice day, all.
Answer
...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"
Also see Markdown footnotes? at Meta. The page mentions Markdown With Footnotes.