adam.nz: # gawk -F, '{print "## "$3,$4; system("grep -i "$3" /etc/passwd | grep -i "$4"

# gawk -F, '{print "## "$3,$4; system("grep -i "$3" /etc/passwd | grep -i "$4" | cut -d: -f1")}' file.csv

Use awk to generate a list of usernames from a CSV list of full names by grepping the passwd file.