Just looked at my 4.0.7 board and the default is Ignore.
Code:
$cell[] = "
<label for=\"v_$user[userid]\"><input type=\"radio\" name=\"validate[$user[userid]]\" value=\"1\" id=\"v_$user[userid]\" tabindex=\"1\" />$vbphrase[accept]</label>
<label for=\"d_$user[userid]\"><input type=\"radio\" name=\"validate[$user[userid]]\" value=\"-1\" id=\"d_$user[userid]\" tabindex=\"1\" />$vbphrase[delete]</label>
<label for=\"i_$user[userid]\"><input type=\"radio\" name=\"validate[$user[userid]]\" value=\"0\" id=\"i_$user[userid]\" tabindex=\"1\" checked=\"checked\" />$vbphrase[ignore]</label>