Duo, formally known as "The Duolingo owl", has passed on. In an Instagram post on Tuesday (12 February), the online language learning app shared the puzzling news with the public. "Authorities are currently investigating his cause of death and we are cooperating fully," the statement read, with Duolingo cheekily insinuating that their mascot most likely died while waiting for users to complete their lessons. Duolingo also asked the public to refrain from sharing why they hate Duo in the comments, noting that the mascot had many enemies. Don't miss: Duolingo reportedly cuts staff in AI shift It added, "If you…