Not an editor, and therefore, I have no experience with this at all.
Anyway, this seems like it would be a no-brainer. If the users can just by-pass the "are you SURE this question hasn't been asked?" thing, and ask their question anyway, then why even HAVE it unless the Authority can confirm it's not a duplicate?
It's not like they're powerless against; they could just open another tab and re-enter the DB and check for themselves. Regardless, I agree with HT.