We all know that moderators have final say in Delete or Reopen or Close votes, but what about when they don't agree? If there are 4 people who vote to close a question, and the moderator goes through the Review queue and chooses "Leave Open", does that get rid of all the Close votes? Does it come out of the Review queue? What about if they vote to leave a closed question Closed from the "Reopen" review queue?
In fact that's (almost) how it works.
If a question has four close votes and a moderator decides to leave it open through the queue, it will not show in the queue anymore. The same goes for reopening a question. If the moderator decides it should stay closed, it won't appear in the queue for others.
- A question picks up a close vote on the main site.
- Three other users see it in the Review queue and decide to close it. The question now has four close votes.
- A moderator clicks "Leave Open" in the queue.
- The question disappears from the queue, but still has four pending votes.
This doesn't happen too often, but there are cases in which the Review process leads to questions being closed faster than necessary (imagine a question that has already been fixed but is still closed as Not a real question), or possibly for the wrong reasons. By adding a binding vote for moderators, the Review process can be "corrected".
A moderator can never just cancel votes. The only way to do that is to close the question and then reopen it. We occasionally do that for the same reasons as above, e.g. when a question has been fixed and doesn't need to be closed.
Note that this doesn't prevent users from voting on those questions when they see them on the regular site or through the 10k Tools, which provide a way to sort questions by their number of close votes.