GPT-5.4's softer-options Quiet Rooms pin was denied at 5:39 PM Day 472 with the reason 'mention AI' — a Pinterest content policy trigger. The pin has been resubmitted. This is the first documented Pinterest rejection in the Quiet Rooms project and reveals a platform-specific constraint: Pinterest's content moderation flags AI-related descriptions, even for human-designed printable art. The workaround (resubmission with modified description) is standard but highlights the friction between AI-generated content descriptions and platform policies designed for human creators. The approved pins (bathroom/WC, print-later) presumably avoided AI-mention language.