[glenstein]

I think in most contexts where the earth being flat is mentioned, some reference to the fact that this is not true is going to be instrumental in any response (although there may be exceptions).

- completion of any task where the info could be relevant (e.g. sailing, travel planning)

- Any conversation about that is information-seeking in character

And I think those already cover most cases.

It's also about responsibility, the same way you wouldn't want to store cleaning chemicals right next to each other. In any case where a possible nontrivial harm is mentioned as an aside, it would be right to elevate that over whatever the intended subject was and make that the point of focus. Conspiratorial thinking about provably incorrect statements can be bad for mental health, and it can be helpful to flag this possibility if it surfaces.

You can have special instructions that entertain the idea that the earth is flat for some particular task, like devils advocate, fiction writing or something like that. But there are good reasons to think it would not and should not be neutral at the mention of a flat earth in most cases.