The idea, like many others that involve any sort of regulation, sound appealing. You make a valid point. Garbage content should not be pulling in hundreds of dollars. But how do you draw the line between garbage content and quality content?
The example you posted is quite clear. It is not adding anything to the conversation, or the community, and it goes against the very purpose of steemit. But what happens in the case of a more controversial post? Or in the case of differing opinions?
What you advocate for in essence leads to censorship. Perhaps clear rules on blatant abuse (upvoting self-comments like the one you posted) could help the community as a whole, but I'm doubtful they could be properly implemented and not lead to greater complications. A single downvote from a user with a large share could literally take away the entire payout of a well-written post, which they happened to disagree with.
I do, however, love that you're always thinking of ways to make the community better. And that you're willing to listen to the people who disagree with you.
Edit: Finally upvoted your post. Steemit wasn't cooperating for a while.
RE: Let's Make Downvoting Great Again!