Comments are good, but it can be annoying to see someone with a huge SP wallet give you a nice comment and skip the upvote.
One of the features of Steemit is the potential reward for contribution to the platform.
While that should not be the only reward (as you said, it is nice to get positive comments as well), a high payout upvote retains contributors.
So we have a balance that I don't see a useful mechanism to maintain: rewarding quality work balanced against curation reward strategies. And we can't discount the draw of curation rewards to investors.
So it does come down to responsible curation by the folks with the fat wallets. If you see something good, upvote it. You can't control the behavior of other curators, and if you try to do that and that results in their reward strategy becoming less efficient, you face the possibility they take their investment out of the platform.