When somebody creates a duplicate node, they do the monestary a disservice, and deserive downvotes. The fact that the disservice is unintentional makes it not as bad, but it doesn't make it OK.

OTOH, if you don't check, and always downvote-and-vote-delete, then the'll get a very low rep, and not just -1. So what should you do? Vote delete, and if there are at least five delete votes, and less then 3 keeps, -- it, because it means that it needs a lower rep to be reaped.

As to your last query, yes. However editors cannot /reap/ nodes, only /delete/ them, outside of the ability to vote "delete" on a consideration, just like anybody else. The difference is that deleted nodes are really /gone/, not just slightly harder to see. (That's not 100% true. A /deleted/ node can be viewed by a god, and if he wishes (all gods are male, at present), he can undelete it. Others, however, cannot even tell that it once existed, by any art known to me.) So, IMnsHO, editoral delete should only be used in extreme cases, and the fact that there is no "editoral reap" that can be appled faster, and does not require negitive rep, is a bug.