Index: site-users.php
===================================================================
--- site-users.php	(revision 25618)
+++ site-users.php	(working copy)
@@ -164,6 +164,13 @@
 $parent_file = 'sites.php';
 $submenu_file = 'sites.php';
 
+/**
+ * Disable showing add existing user form
+ *
+ * @since 3.1.0
+ *
+ * @param  bool true
+ */
 if ( ! wp_is_large_network( 'users' ) && apply_filters( 'show_network_site_users_add_existing_form', true ) )
 	wp_enqueue_script( 'user-suggest' );
 
@@ -243,9 +250,19 @@
 
 </form>
 
-<?php do_action( 'network_site_users_after_list_table', '' );?>
+<?php 
 
-<?php if ( current_user_can( 'promote_users' ) && apply_filters( 'show_network_site_users_add_existing_form', true ) ) : ?>
+/**
+ * Fires after the listing of users table on the network admin
+ *
+ * @since 3.1.0
+ * 
+ */
+do_action( 'network_site_users_after_list_table', '' );?>
+
+<?php 
+//duplicate_hook
+if ( current_user_can( 'promote_users' ) && apply_filters( 'show_network_site_users_add_existing_form', true ) ) : ?>
 <h3 id="add-existing-user"><?php _e( 'Add Existing User' ); ?></h3>
 <form action="site-users.php?action=adduser" id="adduser" method="post">
 	<input type="hidden" name="id" value="<?php echo esc_attr( $id ) ?>" />