There are plenty of comments that may deserve downvoting to remove rewards. Especially when it is low effort trolling, or just plain negativity. Then I think any stakeholder who cares for the platform and experience of the users who add value to Steem should downvote it to remove rewards and make sure it is instead returned to those to bring value.

That being said, I'm completely against big stakeholders being able to hide comments through downvotes, and think that part of steemit is not doing any good. Lastly, I don't know why people would be afraid to comment because of downvotes. It is not like not earning anything on a comment makes you lose something?

In any case, the main use for downvotes will be the many self voters and abusers who look to get away with voting on spammed low effort content/comments. Of which there are plenty.