I recently ran into this and I liked the notification / call to action.
However, do you really want people adding justification for Why This Is Not A Duplicate into the question? IMO, this is promoting Bad Question Writing by creating a Second Class Question: it has to justify it's own existence within the text of the question itself. This creates questions that are wordy, defensive, and conversational. I fell into this trap here.
- I don't like writing Second Class Questions. I want my question to be concise and stand on its own, just like all other Questions.
- I don't want to read questions that defend their existence.
If it's not a duplicate, then why should I have to read the defense? Shouldn't that be irrelevant? I just want to read the question and the answer.
Like I said, I really did like the notification / call to action. But I'll put any defense about "why my question should exist" in a comment. Many others won't, and over time, we'll have more and more questions containing defensive arguments Why This Is Not A Duplicate.
FYI: I think this Answer should exist for many reasons.