This is probably very obvious, but if you vote to close a question which is subsequently edited to improve it (say to clarify how it's different from another one), how do you cancel your vote?
The status-declined tag for Can we have the ability to rescind a close vote before it closes? was... rescinded. It was updated to status-planned on June 10, 2013 and subsequently implemented on July 21, 2013, turning it into status-completed.
Users are now able to "undo" their close-votes in a similar way that one can retract/modify your regular vote to a post. A visual display of close-vote retraction resembles:
The display clearly states that "you have already voted to close this question", with the option to "retract [the] close vote". Once retracted, voting-to-close on that specific is closed to you with a display that summarizes your voting history:
In the light of Stefan's answer, we should have the convention that if you would rescind your vote-to-close then you should leave a comment to the effect saying "I voted to close on an earlier version of this question, I now consider it worth keeping.". We could have the convention that someone else who still thought it worth closing then left a comment saying "I'm taking over X's vote to close.".
On MO, on any question where there's some disagreement, or something a little out of the ordinary, we start a discussion on meta so that people can make their case.
This has been discussed at meta.stackoverflow.com: Can we have the ability to rescind a close vote before it closes?
It's been tagged status-declined.