reverted:
--- b/core/modules/taxonomy/src/Controller/TermAutocompleteController.php
+++ a/core/modules/taxonomy/src/Controller/TermAutocompleteController.php
@@ -9,7 +9,7 @@
 
 use Drupal\Component\Utility\Tags;
 use Drupal\Component\Utility\Unicode;
+use Drupal\Component\Utility\String;
-use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\Query\QueryInterface;
@@ -161,7 +161,7 @@
       foreach ($terms as $term) {
         // Term names containing commas or quotes must be wrapped in quotes.
         $name = Tags::encode($term->getName());
+        $matches[] = array('value' => $prefix . $name, 'label' => String::checkPlain($term->getName()));
-        $matches[] = array('value' => $prefix . $name, 'label' => SafeMarkup::checkPlain($term->getName()));
       }
       return $matches;
     }
reverted:
--- b/core/modules/taxonomy/src/Plugin/Field/FieldFormatter/LinkFormatter.php
+++ a/core/modules/taxonomy/src/Plugin/Field/FieldFormatter/LinkFormatter.php
@@ -8,7 +8,7 @@
 namespace Drupal\taxonomy\Plugin\Field\FieldFormatter;
 
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Component\Utility\String;
-use Drupal\Component\Utility\SafeMarkup;
 use Drupal\taxonomy\Plugin\Field\FieldType\TaxonomyTermReferenceItem;
 
 /**
@@ -34,7 +34,7 @@
     foreach ($items as $delta => $item) {
       if ($item->hasNewEntity()) {
         $elements[$delta] = array(
+          '#markup' => String::checkPlain($item->entity->label()),
-          '#markup' => SafeMarkup::checkPlain($item->entity->label()),
         );
       }
       else {
reverted:
--- b/core/modules/taxonomy/src/Plugin/Field/FieldFormatter/PlainFormatter.php
+++ a/core/modules/taxonomy/src/Plugin/Field/FieldFormatter/PlainFormatter.php
@@ -8,7 +8,7 @@
 namespace Drupal\taxonomy\Plugin\Field\FieldFormatter;
 
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Component\Utility\String;
-use Drupal\Component\Utility\SafeMarkup;
 
 /**
  * Plugin implementation of the 'taxonomy_term_reference_plain' formatter.
@@ -31,7 +31,7 @@
 
     foreach ($items as $delta => $item) {
       $elements[$delta] = array(
+        '#markup' => String::checkPlain($item->entity->label()),
-        '#markup' => SafeMarkup::checkPlain($item->entity->label()),
       );
     }
 
reverted:
--- b/core/modules/taxonomy/src/Tests/TermTest.php
+++ a/core/modules/taxonomy/src/Tests/TermTest.php
@@ -8,7 +8,7 @@
 namespace Drupal\taxonomy\Tests;
 
 use Drupal\Component\Serialization\Json;
+use Drupal\Component\Utility\String;
-use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\Tags;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
@@ -342,8 +342,8 @@
       return $item['label'];
     }, $data);
 
+    $this->assertTrue(in_array(String::checkPlain($first_term->getName()), $data), 'Autocomplete returned the first matching term');
+    $this->assertTrue(in_array(String::checkPlain($second_term->getName()), $data), 'Autocomplete returned the second matching term');
-    $this->assertTrue(in_array(SafeMarkup::checkPlain($first_term->getName()), $data), 'Autocomplete returned the first matching term');
-    $this->assertTrue(in_array(SafeMarkup::checkPlain($second_term->getName()), $data), 'Autocomplete returned the second matching term');
 
     // Try to autocomplete a term name that matches first term.
     // We should only get the first term in a json encoded string.
@@ -351,7 +351,7 @@
     $path = 'taxonomy/autocomplete/node/taxonomy_' . $this->vocabulary->id();
     $this->drupalGet($path, array('query' => array('q' => $input)));
     $target = array(array(
+      'value' => String::checkPlain($first_term->getName()),
-      'value' => SafeMarkup::checkPlain($first_term->getName()),
       'label' => $first_term->getName(),
     ));
     $this->assertRaw(Json::encode($target), 'Autocomplete returns only the expected matching term.');
@@ -364,7 +364,7 @@
     $n = Tags::encode($third_term->getName());
     $target = array(array(
       'value' => $n,
+      'label' => String::checkPlain($third_term->getName()),
-      'label' => SafeMarkup::checkPlain($third_term->getName()),
     ));
     $this->assertRaw(Json::encode($target), 'Autocomplete returns a term containing a comma and a slash.');
   }