[1] https://docs.python.org/devguide/faq.html#where-can-i-learn-...
It's a bit of a toughie, the python community doesn't have much to deal with Markdown itself. pypi expects rst etc. There's also very few tools available in general, which is a huge shame.
Part of this is due to different Markdown "flavours". At this point though, Github being the largest provider of Markdown, a safe bet would be to standardize on Github's flavour and call it a day.
That's true: According to Wikipedia RST is from 2002 (so is AsciiDoc), Markdown from 2004. Perhaps also important though is that RST was introduced as a direct successor to StructuredText, which apparently, had some currency in the Python community previously.
Furthermore, the document structure in rst is far more powerful (e.g., you choose your heading conventions).
As it turns out, I am not actually a huge fan of python (and there are plenty of problems with rst), but in the comparison between mdown and rst, the only argument I actually see in favor of mdown is that it's more commonly used (though the fact that commonmark has yet to completely take over actually mitigates that a fair bit).
The syntax is horrible.
However, this is jumping into completely subjective territory; you, of course, do not have to like rst, just as I do not have to like mdown. So, I will stick with my original sentiment of wishing these services would support the thing I like :)
Rst feels like a happy medium between mdown and LaTeX for me, which is actually very much how I use it. I use it in situations where I would have used LaTeX in the past (instances where mdown surely wouldn't cut it). Of course, there are some times (e.g., tables, figures and bibliographies) where LaTeX is the only sensible option, but for anything simpler, I'd still prefer the power that Rst gives me.
Additionally, I actually really like most of how Rst does URLs. It is definitely less simple than mdown, but it's so much more powerful and generalized.
http://commonmark.org/. Of course, you might already know about this, and just be playing the https://xkcd.com/927/ card.
On that topic, does anyone know what flavour of markdown is being used here (in fiddle.md)?