California-born skier Eileen Gu , who won Olympic gold for China, gushed on Instagram about the ease of ducking social media censorship in her adopted nation. Then her post vanished, apparently a result of censorship . Gus chirpy Instagram posts during the Olympics have touched off furious debate in China, where the government blocks Instagram, as well as Google, Facebook, Twitter and WhatsApp, in its so-called Great Firewall. Why can you use Instagram and millions of Chinese people from the mainland cannot? an angry follower asked Gu last week in a post. Gu seemed surprised by the question, suggesting it…