When asking a question through the iOS app (v. 0.1.24), the question just gets posted without any sort of chance to review similar questions. (This is shown on the iOS web app and desktop browsers on the full site in the right sidebar as you edit any question before posting it.)
Would it be possible to have new questions saved as drafts (ideally to the servers), and then present a second sheet with potential duplicates?
This would let someone compose a question and then encourage them to make sure it's not already machine matched with a similar post before it actually gets posted to the site.