When Jen Jack Gieseking started researching his book on queer nightlife in New York, he learned that one of the city’s hottest lesbian watering holes was not a bar at all. Sure, participants had fond memories of dancing and flirting at historically lesbian bars. But if the queer women and transgender and nonbinary people in Gieseking’s focus groups really wanted to catch up on the latest gossip, there was only one place to go: the Park Slope Food Co-op, a collectively owned and operated grocery store in Brooklyn. “Amusingly, participants…