Rahul Vohra took Superhuman from 22% to above the 40% product-market fit threshold with one survey question. The question he added: "What type of people would benefit most from this?" Nine extra words on a survey they'd been running for months. Happy users described themselves. Their self-descriptions became Superhuman's ICP. The positioning and roadmap narrowed around what those answers said. That's the part most PMs miss. A good survey reveals who your market is, not whether they like…