I've noticed that after a question is closed, users still have the change to flag it. The only difference is the "it doesn't belong here" sections is removed. We still have the option to flag it as spam, offensive ("not welcome in our community"), very low quality, or other.
One one level this makes sense, since (valid) flags on a closed post probably mean it is a candidate for deletion, and these are the flags that typically mean a(n open) question is a candidate for deletion.
However, since this question was flagged and closed or voted to be closed by users with appropriate rep, it doesn't seem necessary to have all these flags.
- If the post is spam, it would likely be deleted rather than closed.
- If the post is offensive, it would likely be deleted rather than closed.
- If the post is very low quality, it was likely closed for being very low quality, and this flag is redundant.
- The "other" option is, I believe, necessary in any flagging situation, since some un-anticipated case may arise which is not covered by the pre-listed cases.
I suggest the flag options on closed questions be reduced to 2 or 3 options:
- The changes to this post since it has been closed are not constructive, or are not improvements.
- (Maybe. I don't think this one is necessary, but I'm just being thorough) This post has been closed for {a long time}, and has not been improved in any way.
- Other
Since the ultimate result of a closed question should be either that the question is removed via deletion or migration due to being a bad fit for where it was asked, or that the question is reopened due to improvement, these options should cover all the reasons a closed question would need moderator attention.