When I view the page source (always a good first step in debugging why images won't show on a page), I see tags like

<img src="webkit-fake-url://5212E7C3-2AB0-4C87-BA79-7CFA7AA54052/image.tiff" alt="">

... these are almost certainly not what you wanted. (And tiffs won't render in almost anyone's browser.) It appears the WYSIWYG editor is not doing what you wanted.

In this post, Lukeprog hosted the image on his own site and then included it in the post with this code fragment:

<a href="http://commonsenseatheism.com/wp-content/uploads/2011/04/metaethics-flowchart-smaller.png"><img src="http://commonsenseatheism.com/wp-content/uploads/2011/04/metaethics-flowchart-smallest.png" alt=""></a>

Suggestion: if you don't have your own hosting to use, put the image on tinypic.com or somewhere similar (an image host that's okay with hotlinking), and transclude it from there. I'm not sure how to do this in the LessWrong editor, you may have to edit the HTML.