Check out the companies making headlines in midday trading Thursday. Coinbase – The cryptocurrency exchange was up 9.6% after Oppenheimer said Coinbase was well-positioned while the larger sector was having its "Lehman Brothers moment." The failed deal between Binance and FTX caused a "calamitous hurricane," the firm said. Rivian – The electric vehicle maker jumped 18% after the company reported a smaller-than-expected quarterly loss and said its production would remain on track despite supply chain snafus. Six Flags – Shares of the theme park operator surged 13%. It missed top and bottom line expectations when reporting quarterly results, but announced…