You could definitely query for all the rejected projects where the Arbiter returned the funds to the Patron because the work was crap or fake. But that tells you the bad Free Agents.

There sort of wouldn't be "fake projects". A Patron has to pay the project amount in escrow to the Arbiter before a Free Agent worker can be assigned , so once that happens there is skin in the game.

I suppose you could check for Patrons who initiate tons of spam projects and never finalize the escrow... But I don't see that happening a ton.

The real thing you'd want to be vigilant for is Arbiters who abscond with the escrow! You'd query that by looking for work submissions that don't ever have a correspondening payment NOR refund.

TL;DR: I'd like if the whole reputation picture can just be gleaned from the event trail without requiring reports or anything like that. Maybe an Arbiter somewhere sets up a DVM that does these queries routinely in order to prove to the market that they are among the most trustworthy. He could charge for that DVM - almost like a licensing board, but nobody has to pay attention to it if they don't care.