Why is it possible to keep downvoting closed questions?

Question

Say someone asked a question, that seemed legit to him at the moment.
The community thought otherwise and downvoted him and from some (good) reason, the question was closed.

Why is it still possible to keep downvoting the question?

Answer 1

Downvoting and closing are two separate things:

^{[image source: Shog9]}

A closed question may still be upvoted, although it's a rare case that an off-topic thing is still popular. A question may also be heavily downvoted despite not being closed. There's a clear separation between the two axes on that diagram. So the system allows up/down voting on closed questions as well as open ones. That way, we can see the difference between "terrible off-topic question" (very low score, closed) and "bad off-topic question" (quite low score, closed) and "question which is OK but just happens to be off-topic" (score not bad, closed).

At least in theory ... in practice, of course, voting is a bit harder to predict and not always exactly tied to post quality ...

Answer 2

Just to add onto Rand's answer because it was getting a bit long for a comment and I think it warranted an answer.

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Look at this a different way, would you want to stop people from upvoting questions that are closed? I suspect that you wouldn't but then why should someone be allowed to upvote but not downvote?

There are still viable reasons for voting in either direction because it is closed. For example, one might upvote a question closed as a duplicate because it is still a good question and a good duplicate is generally a good question. One might also upvote a question that they believe is good and wrongfully closed. There are any number of reasons.

The same applies in the other direction, for downvoting too. There are again many reasons which correlate to the same reasons one would downvote an open question. There are a couple of things I would like to point out though which help the system:

• Downvoting a question to -4 or below means it won't show up on the homepage. In some, (hopefully) rare, cases this is desirable so that as few as people as possible see the post.

• If the question is downvoted enough and closed the automatic script will come along and "clean up" (delete) the question in some cases. Therefore, downvoting in cases like this helps the system be clean and streamlined.