MAI SHAMS ELDIN  WHEN dozens of Egyptians began posting accounts of sexual assault on social media last month, activists sensed a "#MeToo" moment in a nation where women have long felt disadvantaged. Like high-profile trials in the United States where the now global women's rights hashtag took off, prosecutors launched charges in Egypt's best-known recent case: a student from a wealthy background facing multiple accusations. To encourage victims to come forward, the government approved a bill to better protect their identity. Yet when the administrator of the Instagram page that attracted the first testimonies tried to expose a second high-profile…