What is the significance of not seeing the sun [and not knowing]?
Rashi: The Nefel did not desire.
Ibn Ezra: The Nefel did not toil in worldly matters.
Rashbam: This hints to "Nefel Eshes Bal Chazu Shamesh" (Tehilim 58:9).
Seforno: The Nefel cannot be pained over loss of any purpose.
Metzudas David: It did not know that there is more contentment from one matter more than from another, therefore it is not pained over lack of good. The man knew what is good; he is pained greatly that it is missing from him.
Why does the Nefel have more Nachas than the man of verse 3?
Refer to 6:5:1:1.
Ibn Ezra, Ri Kara: The Nefel did not toil. The man toiled, without rest, and has no reward or pleasure in both worlds.
Rashbam: The man knew only evil; the Nefel did not know good or evil (5).