I seriously doubt duplicating a question will be banned in 2024, or in any near-future year.
I do believe that duplicates of a question will be de-emphasized or otherwise filtered down to one or two blessed variants that are presented to more users. There is even a Notion document from the Manifold team with ideas about how to mark/tag/track duplicates.
They did introduce a guideline against needlessly duplicating questions: /firstuserhere/will-manifold-introduce-a-rule-or-a , but i don't think that duplicating should be banned, it's a very useful functionality. It lets us use a market as a template and save wasted effort. GitHub also lets people fork repositories and that's just fine.
I don't see a problem here, because troll duplications trying to take advantage of the system are unranked and unsubsidized.
Thinking of duplication as "Using markets as a template" should be a better framing.