A great deal of LLM-generated content shows up in comments on social media. That's going to be hard to classify with a system like this and it will get harder as time goes on.
Another interesting trend is false accusations of LLM use as a form of attack.
Unlike other user-report detection (e.g. medical misinformation), this swims in the same direction as most AI misinformation. User-reported detection is typically going against the stream of misinformation by countering coordinated campaigns and pointing the user to a verifiable base truth. In this case there's no easy way to verify the truth. And the big state actors who are known to use LLMs in misinformation campaigns are battling the US for AI supremacy and so have an incentive to attack the US on AI since it's currently in the lead.
Especially if you're relying on volunteers, this seems prone to abuse in the same way, e.g. Reddit mods are. Thankless volunteer jobs that allow changing the conversation are going to invite misinformation farms or LLM farms to become enthusiastic contributors.