I really want to see flagging normalized. If those who are upvoting valueless content feared flags, they would think more carefully about promoting content they thought might get flagged.
I don't understand it at a code level, but common sense says, if I have 10 votes a day, and I spend 11 (one flag) that has to come from somewhere. It has to be paid for in terms of stake and resource credits... doesn't it?
Downvotes would still use RC, so in that sense they wouldn't be completely 'free' and do indeed use resources at the code level, but would be far less expensive than the status quo where every downvote costs you an upvote.