Fairly sure that this is never going to happen, nor do I think it should, unless you're describing duplicate content sent to the same community on the same instance within a certain period.

The fediverse is decentralized and by design each instance is independent. Data is shared between instances depending on subscribers. There isn't a central database for every post or comment.

A person posting the same content on two instances would each automatically distribute that to other instances. At some point there'd be overlap when the duplicate content arrived at the same instance.

At that point, which one is duplicate and which one is original? Do you delete the duplicate? What about the other instances that already have the content?

Do you want to introduce a definitive source of truth that tracks which post was first? Doing so creates a single point of censorship and failure.

So, I'm going with, no, that's not something I think can, or should ever happen.