diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -13,10 +13,8 @@
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\Unicode;
-use Drupal\Component\Utility\Xss;
 use Drupal\Core\Config\Config;
 use Drupal\Core\Config\StorageException;
-use Drupal\Core\Render\SafeString;
 use Drupal\Core\Template\Attribute;
 use Drupal\Core\Theme\ThemeSettings;
 use Drupal\Component\Utility\NestedArray;
@@ -1067,25 +1065,6 @@
 }
 
 /**
- * Prepares variables for inline list templates.
- *
- * Default template: inline-list.html.twig.
- *
- * @param array $variables
- *   An associative array containing:
- *   - items: An array of items to be displayed in the list.
- *   - separator: A string to separate list items.
- *   - empty: A message to display when there are no items.
- *
- * @see https://www.drupal.org/node/1842756
- */
-function template_preprocess_inline_list(&$variables) {
-  // Since the separator may be user-specified, it must be filtered to permit
-  // some HTML (such as <br />) to pass through.
-  $variables['separator'] = SafeString::create(Xss::filter($variables['separator'], ['br']));
-}
-
-/**
  * Returns HTML for an indentation div; used for drag and drop tables.
  *
  * @param $variables
@@ -1751,7 +1730,7 @@
       'variables' => array('items' => array(), 'title' => '', 'list_type' => 'ul', 'attributes' => array(), 'empty' => NULL, 'context' => array()),
     ),
     'inline_list' => array(
-      'variables' => array('items' => array(), 'separator' => ', ', 'attributes' => array(), 'empty' => NULL),
+      'variables' => array('items' => array(), 'separator' => ', '),
     ),
     'feed_icon' => array(
       'variables' => array('url' => NULL, 'title' => NULL),
diff -u b/core/modules/system/src/Tests/Theme/FunctionsTest.php b/core/modules/system/src/Tests/Theme/FunctionsTest.php
--- b/core/modules/system/src/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/src/Tests/Theme/FunctionsTest.php
@@ -176,39 +176,18 @@
     $expected = '';
     $this->assertThemeOutput('inline_list', $variables, $expected, 'Empty %callback generates no output.');
 
-    // Verify that empty items produce the empty string.
+    // Verify that elements are correctly delimited by commas by default.
     $variables = array();
-    $variables['empty'] = 'No items found.';
-    $expected = 'No items found.';
-    $this->assertThemeOutput('inline_list', $variables, $expected, 'Empty %callback generates empty string.');
-
-    // Verify that empty text is not displayed when there are list items.
-    $variables = array();
-    $variables['empty'] = 'No items found.';
     $variables['items'] = array('Rabbit', 'rabbit', 'rabbit');
     $expected = 'Rabbit, rabbit, rabbit';
-    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback does not print empty text when there are list items.');
-
-    // Verify that a non-default separator is rendered.
-    $variables = array();
-    $variables['items'] = array('Un', 'Deux', 'Trois');
-    $variables['separator'] = ' and ';
-    $expected = 'Un and Deux and Trois';
-    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback uses a custom separator when provided.');
+    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback elements are correctly delimited by commas by default.');
 
-    // Verify that HTML separators are properly rendered.
+    // Verify that HTML separators are escaped.
     $variables = array();
     $variables['items'] = array('Doe', 'Buck', 'Kit');
-    $variables['separator'] = '<br />';
-    $expected = 'Doe<br />Buck<br />Kit';
+    $variables['separator'] = '&lt;br /gt;';
+    $expected = 'Doe&lt;br /&gt;Buck&lt;br /gt;Kit';
     $this->assertThemeOutput('inline_list', $variables, $expected, '%callback allows HTML in user-provided separators.');
-
-    // Verify that the separator is sanitized.
-    $variables = array();
-    $variables['items'] = array('Un', 'Deux', 'Trois');
-    $variables['separator'] = '<script>alert("test")</script>';
-    $expected = 'Unalert("test")Deuxalert("test")Trois';
-    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback sanitizes user-provided separators.');
   }
 
   /**
diff -u b/core/modules/system/templates/inline-list.html.twig b/core/modules/system/templates/inline-list.html.twig
--- b/core/modules/system/templates/inline-list.html.twig
+++ b/core/modules/system/templates/inline-list.html.twig
@@ -3,18 +3,14 @@
  * @file
- * Default theme implementation for an inline list of items.
+ * Default theme implementation for a comma-delimited list of items.
  *
  * Available variables:
  * - items: A list of items.
- * - separator: A delimiter to separate the items in the list.
- * - empty: A message to display when there are no items.
- *
- * @see template_preprocess_inline_list()
+ * - separator: A delimiter to separate the items in the list. Defaults
+ *   to a comma followed by a space (", ").
  *
  * @ingroup themeable
  */
 #}
 {%- for item in items -%}
   {{ item }}{{ loop.last ? '' : separator }}
-{%- else -%}
-  {{- empty -}}
 {%- endfor -%}