Readers can't identify watermarked AI text

In the last few weeks, I’ve been complaining that everyone is wrong about AI watermarking: it isn’t really anti-consumer and it doesn’t make the outputs any worse. The watermarking papers demonstrate1 that this is true, but I thought it might be interesting to put it to a practical test. Given examples of watermarked and unwatermarked answers to the same prompt, could readers tell which is which? To find out, I vibed up2 https://sgoedecke.github.io/watermark-quiz/, a static site that quizzes readers. I used Qwen3-30B-A3B-Instruct-2507 on a rented H200 to generate thirty responses: three responses per question, one of which was secretly watermarked with SynthID-Text. The rented GPU cost around two dollars. To measure results, I just sent users to a different page for each score, and aggregated visitors-per-page in my analytics3. This would be easily spoofable if anyone cared enough to do so, but for a casual test I think it’s acceptable. The first round of traffic I got to the quiz…