diff --git a/core/includes/config.inc b/core/includes/config.inc
index 522abbd..6652df7 100644
--- a/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -71,15 +71,25 @@ function config($name) {
 /**
  * Retrieves a configuration object for administration.
  *
- * This configuration object has a special configuration context (admin = TRUE)
- * and configuration plug-ins should mostly keep hands off this object and don't
- * override it.
+ * This configuration object will be created using a special configuration
+ * context (config.admin = TRUE) and configuration plug-ins should mostly keep
+ * hands off it and don't override it.
+ *
+ * This is intended for administration forms or any other case when we need to
+ * get / set the configuration data without any overrides, as oppossed to
+ * regular configuration used for runtime operations that may be altered by
+ * plug-ins depending on other page request parameters:
+ *
+ * To get regular configuration objects for the page request use config()
+ * instead of this function.
  *
  * @param $name
  *   The name of the configuration object to retrieve.
  *
  * @return Drupal\Core\Config\Config
  *   A configuration object.
+ *
+ * @see config()
  */
 function config_admin($name) {
   static $config_factory;
@@ -92,6 +102,17 @@ function config_admin($name) {
 /**
  * Retrieves a configuration factory object for a given context.
  *
+ * A configuration context is an array of parameters that are available to the
+ * configuration plug-ins for them to customize the configuration data in
+ * different ways. Examples of parameters used by Drupal core are:
+ * - 'user.account', to get configuration that may be localized for a user.
+ * - 'config.admin', TRUE to get configuration data without further
+ *   customizations for administration purposes.
+ *
+ * Modules can add any other parameter or provide plug-ins that react to
+ * specific context parameters. In order to avoid conflicts the parameter
+ * keys should be prefixed by the module name.
+ *
  * @param array $context
  *   (optional) Array with contextual data to be used for the configuration
  *   factory. Defaults to an empty array.
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index a52e1af..a6458ac 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -1072,7 +1072,7 @@ function locale_config_factory(ConfigFactory $factory) {
   if (!$factory->getContext('locale.language')) {
     // Add user's language for user context.
     if ($account = $factory->getContext('user.account')) {
-      $factory->setContext('locale.language', user_preferred_language($account));
+      $factory->setContext('locale.language', language_load(user_preferred_langcode($account)));
     }
   }
 }
diff --git a/core/modules/user/user.admin.inc b/core/modules/user/user.admin.inc
index 396f4c0..76f697f 100644
--- a/core/modules/user/user.admin.inc
+++ b/core/modules/user/user.admin.inc
@@ -270,8 +270,8 @@ function user_admin_account_validate($form, &$form_state) {
  * @see user_admin_settings_submit()
  */
 function user_admin_settings($form, &$form_state) {
-  $config = config('user.settings');
-  $mail_config = config('user.mail');
+  $config = config_admin('user.settings');
+  $mail_config = config_admin('user.mail');
 
   // Settings for anonymous users.
   $form['anonymous_settings'] = array(
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index b7ac23d..6614bdc 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -2083,35 +2083,21 @@ function user_view_multiple($accounts, $view_mode = 'full', $langcode = NULL) {
 function user_mail($key, &$message, $params) {
   $langcode = $message['langcode'];
   $variables = array('user' => $params['account']);
-  $message['subject'] .= _user_mail_text($key . '.subject', $langcode, $variables);
-  $message['body'][] = _user_mail_text($key . '.body', $langcode, $variables);
-}
-
-/**
- * Returns a mail string for a variable name.
- *
- * @param string $key
- *   The config key that provides the mail text.
- * @param string $langcode
- *   (optional) A language code to use to generate the e-mail text.
- * @param array $variables
- *   (optional) An array of token keys and values.
- *
- * @return
- *   A string value containing the text for the user.mail config key.
- */
-function _user_mail_text($key, $langcode = NULL, $variables = array()) {
+  // Get a configuration object customized for this user, that may be localized
+  // for the user's language.
+  $mail_config = config_factory(array('user.account' => $params['account']))->get('user.mail')->load();
   // We do not sanitize the token replacement, since the output of this
   // replacement is intended for an e-mail message, not a web browser.
-  return token_replace(config('user.mail')->get($key), $variables, array('langcode' => $langcode, 'callback' => 'user_mail_tokens', 'sanitize' => FALSE, 'clear' => TRUE));
+  $token_options = array('langcode' => $langcode, 'callback' => 'user_mail_tokens', 'sanitize' => FALSE, 'clear' => TRUE);
+  $message['subject'] .= token_replace($mail_config->get($key . '.subject'), $variables, $token_options);
+  $message['body'][] = token_replace($mail_config->get($key . '.body'), $variables, $token_options);
 }
 
 /**
  * Token callback to add unsafe tokens for user mails.
  *
- * This function is used by the token_replace() call at the end of
- * _user_mail_text() to set up some additional tokens that can be
- * used in email messages generated by user_mail().
+ * This function is used by the token_replace() to set up some additional
+ * tokens that can be used in email messages generated by user_mail().
  *
  * @param $replacements
  *   An associative array variable containing mappings from token names to