For what I understand, SO is based on the Wisdom of Crowds which says that the aggregation of information in groups result in decisions that are often better than could have been made by any single member of the group. This is also known as Condorcet's jury theorem.
But what may have been forgotten on SO, is this requires a large number of people to vote or to give their opinion, for it to be effective.
What I mean is a question can be closed and even deleted with very few votes, and then very few people can still see them to make them "undeleted".
I would like that the number of votes required to close and delete a question to be significantly raised (something like 50 or even 100 votes).
If this was not possible for any reasons, it would be at least a great improvement if a comment explaining the decision to downvote or to vote for deletion was mandatory (not only a selection in a drop down list) because in each category, there are still many different reasons. For example, what is say in a question may be not correct, or only the way it is said is incorrect, and it would only need to be rephrased to be judged as correct.
P.S. : sorry for my english, I'm not a native speaker, please edit if some sentences don't make sense.