* Update 2012-12-11: Today github has superseded the full correspondence of gist.github.com , and this is no longer a problem. See the screenshot for proof. *
It looks intentional. It is worth noting that syntax highlighting still works in attachments, but not (alas) markdown rendering.
A potential workaround would be to add additional JS code (after the gist embedded JS code) that displays the client database, possibly through http://www.showdown.im/
I made a question for myself to do this for the redmine gist implementation plugin that I wrote. https://github.com/dergachev/redmine_gist/issues/3
Perhaps by the time you read this, I decided to do it :)
Dergachev
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