"*" in pw_passwd prevents pam_unix from changing the password. This is currently not implemented for "*" in sp_pwdp when _unix_shadowed(). Version-Release number of selected component (if applicable): pam-0.99.7.1-2.fc7
It was decided by upstream that this shouldn't be implemented. Also the '"*" in pw_passwd prevents pam_unix from changing the password' feature is now removed from upstream sources.