Duolingo (NASDAQ:DUOL) is a company really taking off today. Despite the overall market being up considerably today, investors may look at the 14% surge in DUOL stock this afternoon and wonder what the company is doing to propel so much investor interest.Well, the online language learning company just released its second-quarter earnings to the cheer of investors. On the revenue front, Duolingo brought in $178.3 million, higher than the$177.1 million analysts had penciled in. But it was really the company’ ...