diff -u b/core/lib/Drupal/Core/Session/AccountInterface.php b/core/lib/Drupal/Core/Session/AccountInterface.php
--- b/core/lib/Drupal/Core/Session/AccountInterface.php
+++ b/core/lib/Drupal/Core/Session/AccountInterface.php
@@ -109,11 +109,11 @@
    * Returns the username of this account.
    *
    * @return
-   *   An unsanitized string with the username to display.
+   *   An unsanitized plain-text string with the username to display.
    *
    * @deprecated in Drupal 8.0.0, will be removed before Drupal 9.0.0.
    *   Use Drupal\Core\Session\AccountInterface::getAccountName() or
-   *   \Drupal\user\RoleInterface::getDisplayName8) instead.
+   *   \Drupal\user\RoleInterface::getDisplayName() instead.
    */
   public function getUsername();
 
@@ -121,7 +121,7 @@
    * Returns the unaltered name of this account.
    *
    * @return
-   *   An unsanitized string with the username to display.
+   *   An unsanitized plain-text string with the username to display.
    */
   public function getAccountName();
 
@@ -129,15 +129,16 @@
    * Returns the display name of this account.
    *
    * By default, the passed-in object's 'name' property is used if it exists, or
-   * else, the site-defined value for the 'anonymous' variable. However, a module
-   * may override this by implementing
+   * else, the site-defined value for the 'anonymous' variable. However, a
+   * module may override this by implementing
    * hook_user_format_name_alter(&$name, $account).
    *
    * @see hook_user_format_name_alter()
    *
    * @return string|\Drupal\Component\Utility\SafeStringInterface
-   *   Either a string that will be autoescaped or a SafeString object that is
-   *   already escaped. Both are safe to be printed.
+   *   Either a string that will be auto-escaped on output or a
+   *   SafeStringInterface object that is already HTML escaped. Either is safe
+   *   to be printed within HTML fragments.
    */
   public function getDisplayName();
 
diff -u b/core/modules/user/user.api.php b/core/modules/user/user.api.php
--- b/core/modules/user/user.api.php
+++ b/core/modules/user/user.api.php
@@ -107,12 +107,12 @@
 /**
  * Alter the username that is displayed for a user.
  *
- * Called by $user->getDisplayName() to allow modules to alter the username that's
- * displayed. Can be used to ensure user privacy in situations where
+ * Called by $account->getDisplayName() to allow modules to alter the username
+ * that is displayed. Can be used to ensure user privacy in situations where
  * $account->name is too revealing.
  *
  * @param string $name
- *   The string that $user->getDisplayName() will return.
+ *   The string that $account->getDisplayName() will return.
  *
  * @param $account
  *   The account object passed to user_format_name().