I wonder why password field still displayed in signup form even if I have set //$closeRegister=1;
from the manual, if the value set at 1, there will be no password field displayed in signup form, user's password will be sent via email. Why the password field still shown in signup form? What's wrong with my setup options?

My setup options:
/* New options for miniBB 1.6 */
//$metaLocation='go';
//$closeRegister=1;
//$timeDiff=21600;

From the manual:

Note for PHP newbies: //$a='b'; string actually means nothing, and this setting will not work in any case, because this statement is COMMENTED (two slashes before). Removing slashes means UNCOMMENT or ENABLE this setting.

Searching on forums is also useful:

$closeRegister and actions needed to take around, when you enable it