Host Nato Green runs his Iron Comic competition like a well-oiled machine. Last night’s event at San Francisco Punchline featured one visitor and four local favorites, with Sean Keane defending the title. The idea is simple: five comics compete for three rounds, doing extemporaneous material on whatever topics they are given. They’re judged by a panel of — ahem — experts on wit, creativity, carriage, cadence, delivery, posture, and humor. The final two go head-to-head in a death match, in which the audience votes by applause. Then they have to answer questions about what’s important to them and how they would change the world. (Just kidding, Green handles that part.) Last night’s judge panel included San Francisco supervisor David Chiu, comedian Ali Wong, and yours truly. It was a night for bloodsport.