But would increasing voting frequency make the content better? It seems to me equally likely that it would make it worse. Ditto for having a more prominent submit link.
There is a submission bookmarklet. There's a link to it at the bottom of the page.
Yes, it seems equally likely that it would make things worse. But it seems unlikely that it would have no effect. It is unlikely that these are the optimal shapes of the up and down buttons.
For what it's worth, I think the Google way to solve this would be to figure out which metrics you can associate with quality and A/B test the impact of the UI changes. Setting up an A/B framework might be more work than you want to put in. But there might be a UI that encourages higher quality that you could discover empirically.
There is a submission bookmarklet. There's a link to it at the bottom of the page.