I mean, the example with "I'm at a planet made of marshmallows" and how the generated text changes from the default I guess style to a bombastic description.

I don't have an example of that in GPT-3 playground right away, but I suppose it works similarly and could be used to nudge the AI writing style in some way.

This is also why I'm not holding any expectations with offering you a story idea; the AI can come up with a story idea, in my experience, once I did not start with "You wake up in a cart in Skyrim" but with mere "You wake up in a carriage" and the AI started to improv right away, "A man in black robe enters the carriage", and I let it continue, chiefly on its own. Though I haven't saved that story, I will remember it well - the mysterious man in black robe locked up the protagonist with a book containing every knowledge of the universe, telling that after a year he'll come back to ask questions; and he came back after a year and asked Deep Philosophical Questions (TM), and the protagonist had not to shabby answers to them; among them stoically accepted death. Subsequently, the mysterious man took the book and left, leaving the room no longer locked. The protagonist traveled to the nearest village and settled to a work as a teacher. Fast forward twenty years later, meeting the black robed figure again, this time it was revealed to be Azrael (the angel of death); only then the protagonist felt truly the fear of death and that changed at least one of the answers to the Deep Philosophical Questions (TM) from the earlier part of the story.

Feel free to use that as a prompt; I doubt the AI will recreate that story with a good writing style with just that, but AI are capricious and one never knows until tries.

I agree that you manually editing to be better written wouldn't have much purpose. I think the point of this exersize is probably "See what an AI can accomplish?" I was reviewing that.