When flagging a question as duplicate, I had this dialog:
This presents a list with 5 items (choices).
I clicked on duplicate of... and I had a list of questions to choose a duplicate:
The label of the dialog is still Why should this question be closed?, the first item is a hint but it's not differentiated from the other items. It has the same style than the question below. In fact it didn't see it on first look and thought it was a proposal of question to mark as source of duplicate. I think it should have a different look or background color to inform the user that this is not a choice but an information box.
Update: I closed my own question so the label is different when flagging some content from another user, it's I am flagging this question because on the main and sub menu.