The page on copyright notices [0] says that every nontrivial file should have copyright notices; however, FSF's recommendation for software under CC0 [1] suggests that such packages technically should contain no copyright notices.
[1] suggest the opposite, where are you reading that a copyright notice should not be attached? [1] https://wiki.creativecommons.org/wiki/CC0_FAQ#May_I_apply_CC0_to_computer_software.3F_If_so.2C_is_there_a_recommended_implementation.3F
