diff --git a/core/modules/user/templates/user-signature.html.twig b/core/modules/user/templates/user-signature.html.twig
index cac3a68..2e8bc0a 100644
--- a/core/modules/user/templates/user-signature.html.twig
+++ b/core/modules/user/templates/user-signature.html.twig
@@ -17,6 +17,6 @@
 #}
 {% spaceless %}
 {% if signature %}
-  <div{{ attributes }}><div>—</div>{{ signature }}</div>
+  <div class="clear {{ attributes.class }}"{{ attributes }}><div>—</div>{{ signature }}</div>
 {% endif %}
 {% endspaceless %}
diff --git a/core/modules/user/templates/user.html.twig b/core/modules/user/templates/user.html.twig
index c7a9a0e..46e6ce9 100644
--- a/core/modules/user/templates/user.html.twig
+++ b/core/modules/user/templates/user.html.twig
@@ -4,22 +4,20 @@
  * Default theme implementation to present all user data.
  *
  * This template is used when viewing a registered user's page,
- * e.g., example.com/user/123. 123 being the users ID.
+ * e.g., example.com/user/123. 123 being the user's ID.
  *
- * Use 'content' to print all content, or print a subset
- *  such as 'content.field_example'.
- * By default, $user_profile['summary'] is provided, which contains data on the
- *  user's history. Other data can be included by modules.
+ * Use 'content' to print all content, or print a subset such as
+ * 'content.field_example'.
  *
  * Available variables:
  *   - content: A list of content items.
  *   - Field variables: for each field instance attached to the user a
- *      corresponding variable is defined; e.g., account.field_example has a
- *      variable 'field_example' defined. When needing to access a field's raw
- *      values, developers/themers are strongly encouraged to use these
- *      variables. Otherwise they will have to explicitly specify the desired
- *      field language, e.g. account.field_example['en'], thus overriding any
- *      language negotiation rule that was previously applied.
+ *     corresponding variable is defined; e.g., account.field_example has a
+ *     variable 'field_example' defined. When needing to access a field's raw
+ *     values, developers/themers are strongly encouraged to use these
+ *     variables. Otherwise they will have to explicitly specify the desired
+ *     field language, e.g. account.field_example.en, thus overriding any
+ *     language negotiation rule that was previously applied.
  *
  * @see template_preprocess()
  * @see template_preprocess_user()
diff --git a/core/modules/user/templates/username.html.twig b/core/modules/user/templates/username.html.twig
index 4524dba..5317014 100644
--- a/core/modules/user/templates/username.html.twig
+++ b/core/modules/user/templates/username.html.twig
@@ -7,7 +7,7 @@
  * - account: The user object to format.
  * - name: The user's name, sanitized.
  * - extra: Additional text to append to the user's name, sanitized.
- * - link: The fully generated link by l if a link_path is set
+ * - link: The link fully generated by l() if link_path is set.
  * - link_path: The path or URL of the user's profile page, home page,
  *   or other desired page to link to for more information about the user.
  * - link_options: An array of options to pass to the l() function's $options
diff --git a/core/modules/user/user.admin.inc b/core/modules/user/user.admin.inc
index aee6ea1..9482f59 100644
--- a/core/modules/user/user.admin.inc
+++ b/core/modules/user/user.admin.inc
@@ -818,7 +818,7 @@ function theme_user_admin_permissions($variables) {
 }
 
 /**
- * Default theme implementation for an individual permission description.
+ * Prepares variables for individual permission description templates.
  *
  * Default template: user-permission-description.html.twig.
  *
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index 3445c10..a5dbdd8 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -731,7 +731,7 @@ function user_template_preprocess_default_variables_alter(&$variables) {
 }
 
 /**
- * Preprocesses variables for username.
+ * Prepares variables for username templates.
  *
  * Default template: username.html.twig.
  *
@@ -741,7 +741,7 @@ function user_template_preprocess_default_variables_alter(&$variables) {
  *     (Drupal\user\Plugin\Core\Entity\User).
  *   - uid: The user uid number.
  *
- * Modules that make any changes to variables like 'name' or 'extra' must insure
+ * Modules that make any changes to variables like 'name' or 'extra' must ensure
  * that the final string is safe to include directly in the output by using
  * check_plain() or filter_xss().
  */
@@ -789,7 +789,17 @@ function template_preprocess_username(&$variables) {
   $variables['link_options']['html'] = TRUE;
   // Set a default class.
   $variables['attributes'] = new Attribute(array('class' => array('username')));
+}
 
+/**
+ * Processes variables for theme_username().
+ *
+ * @see template_preprocess_username()
+ */
+function template_process_username(&$variables) {
+  // Finalize the link_options array for passing to the l() function.
+  // This is done in the process phase so that attributes may be added by
+  // modules or the theme during the preprocess phase.
   if (isset($variables['link_path'])) {
     // $variables['attributes'] contains attributes that should be applied
     // regardless of whether a link is being rendered or not.
@@ -2266,19 +2276,6 @@ function user_build_filter_query(SelectInterface $query) {
 }
 
 /**
- * Preprocess variables for user signature templates.
- *
- * Default template: user-signature.html.twig.
- *
- * @param array $variables
- *   An associative array containing:
- *   - signature: The user's signature.
- */
-function template_preprocess_user_signature(&$variables) {
-  $variables['attributes'] = new Attribute(array('class' => array('clear')));
-}
-
-/**
  * Get the language object preferred by the user. This user preference can
  * be set on the user account editing page, and is only available if there
  * are more than one languages enabled on the site. If the user did not
diff --git a/core/modules/user/user.pages.inc b/core/modules/user/user.pages.inc
index 590d65a..1d6856d 100644
--- a/core/modules/user/user.pages.inc
+++ b/core/modules/user/user.pages.inc
@@ -176,7 +176,7 @@ function user_logout() {
 }
 
 /**
- * Prepares variables for user template.
+ * Prepares variables for user templates.
  *
  * Default template: user.html.twig.
  *
@@ -197,8 +197,7 @@ function template_preprocess_user(&$variables) {
   field_attach_preprocess($account, $variables['elements'], $variables);
 
   // Set up attributes.
-  $variables['attributes'] = array('class' => array('profile'));
-  $variables['attributes'] = new Attribute($variables['attributes']);
+  $variables['attributes'] = new Attribute(array('class' => array('profile')));
 }
 
 /**