‘Hidden Letters’ Review: Sororal Secrets

Throughout history, women have survived the stifling strictures of patriarchy by using their own codes of communication — be it intergenerational secrets, whisper networks or gestures legible only to other women. Several centuries ago, in Jiangyong County in southern China, women went a step further, inventing an entire language that they used to write songs, poetry and furtive missives to one another. This fascinating language, Nushu, is the subject of the documentary “Hidden Letters,” though if you’re expecting an illuminating deep dive into its history, you’ll be disappointed. The director,…