It does cost voting power and grants no curation rewards. That’s the disincentive built into the system to avoid flag abuse.
As I mentioned in another reply, I’m already softening my stance a bit and have been targeting just the content that’s reposting material and including markers such as [oc] in the title. It may have been original content shared on reddit... but if the they’re not bothering to edit that out of their cut & paste sharing then I consider it plagiarism.
I’m torn on the other spammy comic strip shares. They’re mainly just a vehicle for these accounts to direct a few paid bot upvotes to. If I’m feeling extra grumpy I blast them a bit too in hopes it’ll encourage them to keep their little Steem farming operation out of my favorite tag!