Would you like to downvote submissions?

I wouldn't.

And I'm not so sure if I like the possibility of downvoting comments... would be enough with report, as the comment from "missedthecue".

I generally do not like the Idea if giving a feedback (+ or -) without saying why. It is too cheap, and often leads to miss-/ab-use

If something is inappropriate or commercial spam, report it and Dang will remove it pretty quickly. If something doesn't interest you, skip it and read something else. These two options cover all contingencies. Why the need for a downvote button?

I would, I think it would be interesting to see up to down ratios.