Perhaps Hawkmoth tells Chat Noir because he believes Chat Noir can understand his motives or is trying to manipulate him into giving up the miraculous.
Chat Noir might save the fanfiction by using his charm and charisma to inspire the writers. He could visit the authors in their dreams and give them new ideas, thus saving the fanfiction from being dull or unfinished.
The original Chat Noir miraculous story is really exciting. Chat Noir is one of the main characters in the Miraculous universe. He has the power of the Cat Miraculous. He teams up with Ladybug to fight against various villains in Paris. He's a charming and flirty character, often using his cat - like agility and the power of Cataclysm to help in battles.
One consequence could be that he loses his standing as a hero in Paris. People who once looked up to him would see him as a traitor.
Well, in some fanfictions, Hawkmoth might use false promises. He could promise Cat Noir something like the power to save a loved one in exchange for his help.
In many such fanfictions, Chat Noir might get hurt during a fight with a powerful akuma. Maybe he's outnumbered or faces a new and dangerous power. Writers often use this to create drama and show Ladybug's concern for him.
One way is that he could use his super - senses to detect any flaws in the fanfiction's plot. Then, he can somehow communicate with the writer (maybe in a magical way) to suggest improvements. For instance, if there's a lack of action in the story, he can inspire the writer to add some of his signature acrobatic fight scenes.
One possible fanfiction could involve Chat Noir being akumatized after a major argument with Ladybug. Maybe he feels constantly overshadowed or unappreciated. The akuma could enhance his negative feelings, making him more aggressive and less in control. His powers might become distorted, and he could start causing chaos in Paris. Ladybug would then have to find a way to reach out to the real Chat Noir inside the akumatized form and purify the akuma.
Well, he might become a bit more goofy and less focused. He could start chasing after imaginary things or be overly affectionate towards Ladybug in a really comical way. Just like a normal cat would act when affected by catnip.
One common plotline is Ladybug having to take on more responsibility while Chat Noir is injured. She might have to fight akumas alone and also take care of Chat Noir at the same time.
One great Miraculous Ladybug Chat Noir x OC fanfiction is 'The New Hero in Paris'. It has an interesting OC who has unique powers and a great dynamic with Chat Noir. The story is full of action and mystery.