diff --git a/src/applications/config/check/PhabricatorExtraConfigSetupCheck.php b/src/applications/config/check/PhabricatorExtraConfigSetupCheck.php
--- a/src/applications/config/check/PhabricatorExtraConfigSetupCheck.php
+++ b/src/applications/config/check/PhabricatorExtraConfigSetupCheck.php
@@ -167,6 +167,10 @@
     $reply_handler_reason = pht(
       'Reply handlers can no longer be overridden with configuration.');
 
+    $monospace_reason = pht(
+      'Phabricator no longer supports global customization of monospaced '.
+      'fonts.');
+
     $ancient_config += array(
       'phid.external-loaders' =>
         pht(
@@ -245,6 +249,9 @@
       'metamta.precedence-bulk' => pht(
         'Phabricator now always sends transaction mail with '.
         '"Precedence: bulk" to improve deliverability.'),
+
+      'style.monospace' => $monospace_reason,
+      'style.monospace.windows' => $monospace_reason,
     );
 
     return $ancient_config;
diff --git a/src/applications/config/option/PhabricatorSyntaxHighlightingConfigOptions.php b/src/applications/config/option/PhabricatorSyntaxHighlightingConfigOptions.php
--- a/src/applications/config/option/PhabricatorSyntaxHighlightingConfigOptions.php
+++ b/src/applications/config/option/PhabricatorSyntaxHighlightingConfigOptions.php
@@ -137,28 +137,6 @@
         pht(
           "Treat all '*.x.bak' file as '.x'. NOTE: We map to capturing group ".
           "1 by specifying the mapping as '1'")),
-      $this->newOption(
-        'style.monospace',
-        'string',
-        null)
-        ->setLocked(true)
-        ->setSummary(
-          pht('Default monospace font.'))
-        ->setDescription(
-          pht(
-            "Set the default monospaced font style for users who haven't set ".
-            "a custom style.")),
-      $this->newOption(
-        'style.monospace.windows',
-        'string',
-        null)
-        ->setLocked(true)
-        ->setSummary(
-          pht('Default monospace font for clients on Windows.'))
-        ->setDescription(
-          pht(
-            "Set the default monospaced font style for users who haven't set ".
-            "a custom style and are using Windows.")),
     );
   }
 
diff --git a/src/applications/settings/panel/PhabricatorDisplayPreferencesSettingsPanel.php b/src/applications/settings/panel/PhabricatorDisplayPreferencesSettingsPanel.php
--- a/src/applications/settings/panel/PhabricatorDisplayPreferencesSettingsPanel.php
+++ b/src/applications/settings/panel/PhabricatorDisplayPreferencesSettingsPanel.php
@@ -90,8 +90,6 @@
       ),
       pht('User Guide: Configuring an External Editor'));
 
-    $font_default = PhabricatorEnv::getEnvConfig('style.monospace');
-
     $pref_monospaced_textareas_value = $preferences
       ->getPreference($pref_monospaced_textareas);
     if (!$pref_monospaced_textareas_value) {
@@ -139,12 +137,8 @@
         id(new AphrontFormTextControl())
         ->setLabel(pht('Monospaced Font'))
         ->setName($pref_monospaced)
-        // Check plz
-        ->setCaption(hsprintf(
-          '%s<br />(%s: %s)',
-          pht('Overrides default fonts in tools like Differential.'),
-          pht('Default'),
-          $font_default))
+        ->setCaption(
+          pht('Overrides default fonts in tools like Differential.'))
         ->setValue($preferences->getPreference($pref_monospaced)))
       ->appendChild(
         id(new AphrontFormMarkupControl())
diff --git a/src/view/page/PhabricatorStandardPageView.php b/src/view/page/PhabricatorStandardPageView.php
--- a/src/view/page/PhabricatorStandardPageView.php
+++ b/src/view/page/PhabricatorStandardPageView.php
@@ -280,17 +280,14 @@
 
 
   protected function getHead() {
-    $monospaced = PhabricatorEnv::getEnvConfig('style.monospace');
-    $monospaced_win = PhabricatorEnv::getEnvConfig('style.monospace.windows');
+    $monospaced = null;
 
     $request = $this->getRequest();
     if ($request) {
       $user = $request->getUser();
       if ($user) {
-        $pref = $user->loadPreferences()->getPreference(
+        $monospaced = $user->loadPreferences()->getPreference(
             PhabricatorUserPreferences::PREFERENCE_MONOSPACED);
-        $monospaced = nonempty($pref, $monospaced);
-        $monospaced_win = nonempty($pref, $monospaced_win);
       }
     }
 
@@ -306,21 +303,10 @@
         '</style>', $monospaced);
     }
 
-    $font_css_win = null;
-    if (!empty($monospaced_win)) {
-      $font_css_win = hsprintf(
-        '<style type="text/css">'.
-        '.platform-windows .PhabricatorMonospaced, '.
-        '.platform-windows .phabricator-remarkup '.
-          '.remarkup-code-block .remarkup-code { font: %s !important; }'.
-        '</style>', $monospaced_win);
-    }
-
     return hsprintf(
-      '%s%s%s%s',
+      '%s%s%s',
       parent::getHead(),
       $font_css,
-      $font_css_win,
       $response->renderSingleResource('javelin-magical-init', 'phabricator'));
   }