For comparison, I wondered how React would fare. Turns out it can be pretty fast. I did have to use a similar trick of breaking up the line only when the mouse is over it, but the rest is just React's architecture. See the demo here: http://jsfiddle.net/ianobermiller/tZhSp/1/

Edit: updated link, forgot to save

Edit: for more info, React takes care of reusing DOM elements, and also uses event delegation by default.

Edit: for comparision, here is a version without the optimization: http://jsfiddle.net/ianobermiller/QT9Tx/1/