This is the dual form of a question posted by quid: What makes you vote to close a question?
As the entire description in that question is applicable here I avoid adding extra points about why this question is not board and how an acceptable answer may look like. Instead I would like to focus on the subtle aspects of this question that makes it possibly harder to answer in comparison with quid's question.
Voting to close a question may have many trivial reasons like being blatantly off-topic, spam, undergraduate level, homework, etc. But voting to open a question that is already voted to close by deemed rightful voters (who have high enough reputation to be counted as trusted users) possibly needs more strong reasons. I'm really curious to know what such reasons are and what are those parameters that convince a typical person to neutralize others' close-votes by his vote to reopen.
In order to avoid trivial answers like "I vote to reopen because the OP improved the question during an edit after being closed", assume that the original question didn't change that much during the discussion between those who believe it should remain close and those who want it open.