I've thought about Loki's smile and head tilt here a lot and lemme tell you that this is the reaction of someone being recognized and appreciated for who he really is. Odin and everyone else in Loki's life had always suppressed the mischievous part of him and treated it as something damaging and ruinous when in reality all he needed was a guiding hand telling him how to control those powers and use them to help and not hurt. All he needed was reassurance that he CAN be good, he CAN be praiseworthy. This scene is the first time anyone has ever called him "the god of mischief" without any implication that he is evil or wicked or disastrous. He is genuinely happy to be understood for once and for his powers to be considered as something useful and not just damaging. It's also Mobius's earnest behavior and support that made this reassurance possible because Loki is a deeply mistrusting person. Mobius accepted Loki for who he really is from the beginning and tried to guide him through it instead of ignoring that part of him and suppressing it.
