Deryn is not trans, she's a girl who loves flying and the only way to do that during the war and after her family already lost someone during a flight accident is to enlist. The only way to enlist is to be a boy, so she pretends to be one. It's the same argument for making Mulan a trans* character, but that doesn't make it canon.
Deryn has never thought of herself as male, and it's shown through the chapters from her POV always referring to her as a girl and with female pronouns. The only times she gets referred to in narration with male pronouns is when the POV character thinks she is a boy. Apping Deryn as trans is pretty much throwing her canon identity out the window, and even if it's AU, that's a pretty terrible misrepresentation of a character and an identity.
no subject
Deryn has never thought of herself as male, and it's shown through the chapters from her POV always referring to her as a girl and with female pronouns. The only times she gets referred to in narration with male pronouns is when the POV character thinks she is a boy. Apping Deryn as trans is pretty much throwing her canon identity out the window, and even if it's AU, that's a pretty terrible misrepresentation of a character and an identity.