This gives you some of the effect of what I think would be the best solution -- limiting the site's scope significantly -- in that it would give you things which people found interesting but weren't so general that everyone felt they could comment on them.
I think this would work well in conjunction with some of the other ideas in the thread which reduce the number of upvotes people are likely to give (specifically, a cap on the number of upvotes and a visual cap on the display of upvotes).