Who is Seung Sahn from Tao Te Ching and what is their importance?

Translator Stephen Mitchell's old teacher, the Zen Master Seung Sahn, comments on clear water in Chapter 15's notes: adding salt, sugar, or shit to clear water changes it, but originally it is still clear. "No thinking, no mind. No mind, no problem." Seung Sahn is also quoted in notes on chapter 35, saying the Tao has no gate as clear water has no taste and the tongue no bone. "In complete stillness, a stone girl is dancing." On Chapter 50, Seung Sahn comments on coming in and going out empty-handed and having an original face like the shining moon.