I don't think a down-vote is necessary personally....just vote for stuff you like and ignore the rest. However, if there was one, I agree that it shouldn't affect rewards.

Generally, with the flags, I would like the scope for interpretation to be more restricted to a set of community agreed uses. Hopefully that would prevent the flag from being used maliciously or as a means of punishing posts that are not abusive but the account flagging has some other subjective issue with. Ultimately the upvote rewards are enough to enable an initiative to thrive or die off. Obviously we need excellent definitions for abuse, plagiarism and spam.