We hit the nesting limit...
I'd be fine with them putting a down vote arrow that shows negative votes and having that reduce visibility on the trending page. I'd leave the flag there are we need a way to get spam, plagiarism, and obviously abusive stuff to be not visible (unless you look at the block chain). There is a need for a reporting mechanism and I think the flag could work for that.
I simply believe it is a case where mixed messages are being sent.
So people on either side are justified in arguing because it is not a clear message. If it is intended to be a down vote then make it a down arrow and put it in the voting area. If it is intended to be a report bad posts, then change the text to reflect this.
I don't believe it would impact curation at all if there were no down vote at all. How many people like this? That should be a strong indicator. It shouldn't be about me voting down every Barbie Doll post because I have no interest in Barbies. Doing so silences the interest of other people. How many people up vote something is a clear indicator there is interest. SO WHAT if it is not your interest.
If it continues as it is I see it leading to wars... people noting who is down voting things, and retaliatory down voting their things and anything they post. People who down vote any topic they disagree with regardless of quality of content. It could get ugly pretty fast.
We are seeing a little bit of that already.