Maybe something is wrong with me, but the first thing I noticed was the quotes. In fact, from the title posted on HN.
I've had bugs in websites where menus would be completely messed up because they didn't fit in their given space, just because the font of choice was not available on Linux and it fell back on something slightly larger.
Edit: Though in the HN title it is much clearer than in the jsfiddle, for me anyway. Might that be it?