I think ignoring the copy paste comments works just as much as flagging them, they don't even notice if you flag and you might as well use that vp to upvote someone worthy.
You do get a lot of them, seems like more than a lot of people, maybe flagging just encourages them ;-P
Hmmm could that be it? You know what it is, I know some people upvote the stupid copy/paste comments, meaning that slowly, their reputation will increase from those small upvotes. Now if I throw in a flag, that will decrease their reputation somewhat, which makes me feel a lot better than just ignoring them :-)
I sometimes comment on them aswell, which I hope will educate one or two persons. Maybe not, but atleast no one can say I did nothing while the morons took over :D