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"Red leaves, thank books, send feather guests in the wind" are taken from two poems respectively.

One is "thank the red leaves diligently in order to go to the world" in "Title Red Leaves". ,

One is the last couplet in Su Yang's "Two Epics for Xue Nei by Sitting Alone in the Mountain Zhai", "The sunset is still at the top of the mountain, welcoming the breeze."

A hacker is someone who wanders outside.

So the whole sentence means to thank Hongye for sending her thoughts to her relatives in the sky with the wind.