Should a user have to add a comment when they vote to close
The close question feature is clearly broken in my opinion. I see obviously off-topic questions hanging around all the time, it's plain from any short trawls through that questions are being voted for closure for reasons entirely unrelated to their content.
Closing a question is supposed to be done not on a whim, but to keep questions in alignment with the guidelines. Many votes to close are obviously being cast by people who can't or don't read the guidelines (or don't care). They should at least be required to justify themselves. This might help hold them to account, and would help questioners respond/edit appropriately.