No public safety officer shall have any comment adverse to his interest entered in his personnel file, or any other file used for any personnel purposes by his employer, without the public safety officer having first read and signed the instrument containing the adverse comment indicating he is aware of such comment, except that such entry may be made if after reading such instrument the public safety officer refuses to sign it. Should a public safety officer refuse to sign, that fact shall be noted on that document, and signed or initialed by such officer.