BuddyPress.org

Re #1:

Sorry I forget that you need to hook the filter to an action.

Try this:

function snark_reenable_welcome_email() {

remove_filter( 'wpmu_welcome_user_notification', 'bp_core_disable_welcome_email' );

}

add_action('init', 'snark_reenable_welcome_email');

The file is /wp-content/plugins/bp-custom.php