For any discussion on copyright and fair use, we should distinguish between the implications to Copilot the software itself and the implications to users of Copilot.
For Copilot itself, I do see the case for fair use, though it gets fuzzy should Microsoft ever start commercializing the feature. Nevertheless it remains to be seen whether ML training fits the same public policy benefits public libraries and free debate leverages to enable the fair use defense.
For Copilot users, I don't see an easy defense. In your hypothetical, this would be akin to me going on Google books and copying snippets of copyrighted works for my own book. In the case of Google books, they explicitly call out the limits on how the material they publish can be used. I'm contrast, Copilot seems to be designed to encourage such copying, making it more worry some in comparison.
For Copilot itself, I do see the case for fair use, though it gets fuzzy should Microsoft ever start commercializing the feature. Nevertheless it remains to be seen whether ML training fits the same public policy benefits public libraries and free debate leverages to enable the fair use defense.
For Copilot users, I don't see an easy defense. In your hypothetical, this would be akin to me going on Google books and copying snippets of copyrighted works for my own book. In the case of Google books, they explicitly call out the limits on how the material they publish can be used. I'm contrast, Copilot seems to be designed to encourage such copying, making it more worry some in comparison.