Regardless of access rights to the data, I've yet to read a compelling argument why LLMs are even derivative works. You can't identify your Reddit comment in a ChatGPT conversation. How is it any different than a human learning English by reading Reddit? That human wouldn't be violating copyright every time they said a phrase that was repeated by hundreds of Redditors.

My favorite LLM analogy so far is the "lossy jpeg of the web." Within that metaphor, I don't see how anyone can claim copyright on the basis of a pixel they contributed that doesn't even show up in the lossy jpeg. They can't point to it.