I'd rather not do that because then people will start "bumping" stories by commenting "bump" just to promote their personal thing. I think the answer is more users. The site currently gets about 15,000 page views / day which is already amazing given how little promotion the site has had.

Since the site is open source you can see the front page ranking algorithm here: https://github.com/jgrahamc/twostopbits/blob/master/apps/new...