Not a very good UI if it requires a Hacker News story to let me know about it.

But you do now know about it. People telling each other about a hidden feature (via HN or whatever) is a common and valid way for non-essential features to be discovered.

If you designed UIs assuming that that sort of user-to-user education doesn't exist, you'd be forced occasionally to reject a potentially handy power-user feature on the basis that there's no good place to promote it without cluttering the design. Which would be a shame.

Discoverability isn't the be-all/end-all in User Interfaces.

It's just a shortcut, not essential. You have help links in each Markdown-capable textbox anyway.

Press "?" for a list of all keyboard shortcuts ("?" also works on some Google properties).

Unless I've missed something "m" is missing from that help. Odd.

Considering that "m" is half the known keyboard shortcuts (I'm ignoring ? as it represents a recursion I'm unwilling to face right now), that is odd indeed.

I love the idea of treating web-sites more like applications. From a programmer's point of view - yes, keyboard should be a more utilized way of interacting with a web-site, beyond arrow-navigation and filling text-boxes.

Thank you for posting this; I can't tell you how many times I've had to google markdown cheat sheets while using github. This is a huge time saver.

I see people tapping every keys on their keyboard :)

pressing 's' focus on search form ;)

This has been there since the announcement of GFM...

http://github.github.com/github-flavored-markdown/

Markdown Cheat Sheet

On Markdown-enabled portions of the site, press M on your keyboard to display a cheat sheet.

I see. The lightbox content is actually in the page HTML if you view source.

I thought it would let me make a comment like subversion and mercurial do.

On github not git... git commit -m works like in svn btw.

They'll soon need a list (displayed at all times) with all the different shortcuts around the site. Still, very nice idea :)