I spent the day at 'Substack Coachella,' which was full of panels, partying, and old-school magazine vibes Substack threw a party for writers and media founders in New York City. Sydney Bradley/Business Insider My day with Substack began at around 10 a.m. on Thursday, with the platform's CEO, Chris Best, telling a crowd of writers that they "deserve to get rich" and "have fun." It ended a little past 10 p.m. at a podcast studio office space with Substack cofounder Hamish McKenzie , eating pizza with the lingering media folk. Substack's big day was its first-ever media summit — "The Once and Future Media Forum" — that brought together the newsletter platform's content creators, journalists (like me), and founders of new media startups in a sprawling five-story building in the center of SoHo, in New York City. Feed Me's Emily Sundberg kicked off Substack's series of panels by interviewing TBPN's president, Dylan Abruscato, about the tech talk show and its acquisition by OpenAI .…