Index: src/markup/engine/__tests__/remarkup/interpreter-test.txt
===================================================================
--- src/markup/engine/__tests__/remarkup/interpreter-test.txt
+++ src/markup/engine/__tests__/remarkup/interpreter-test.txt
@@ -1,7 +1,7 @@
 phutil_test_block_interpreter (foo=bar) {{{
 content
 }}}
- 
+
 phutil_test_block_interpreter {{{ content
 content }}}
 
@@ -9,37 +9,37 @@
 
 phutil_fake_test_block_interpreter {{{ content }}}
 ~~~~~~~~~~
-Content: content
-Argv: foo=bar
+Content: (content)
+Argv: (foo=bar)
 
 
 
-Content:  content
-content 
-Argv: 
+Content: ( content
+content )
+Argv: ()
 
 
 
-Content:  content 
-Argv: 
+Content: ( content )
+Argv: ()
 
 
 
-<div style="color: red;">No interpreter found: phutil_fake_test_block_interpreter</div>
+<div class="remarkup-interpreter-error">No interpreter found: phutil_fake_test_block_interpreter</div>
 ~~~~~~~~~~
-Content: content
-Argv: foo=bar
+Content: (content)
+Argv: (foo=bar)
 
 
 
-Content:  content
-content 
-Argv: 
+Content: ( content
+content )
+Argv: ()
 
 
 
-Content:  content 
-Argv: 
+Content: ( content )
+Argv: ()
 
 
 
Index: src/markup/engine/remarkup/blockrule/PhutilRemarkupBlockInterpreter.php
===================================================================
--- src/markup/engine/remarkup/blockrule/PhutilRemarkupBlockInterpreter.php
+++ src/markup/engine/remarkup/blockrule/PhutilRemarkupBlockInterpreter.php
@@ -6,6 +6,17 @@
  */
 abstract class PhutilRemarkupBlockInterpreter {
 
+  private $engine;
+
+  final public function setEngine($engine) {
+    $this->engine = $engine;
+    return $this;
+  }
+
+  final public function getEngine() {
+    return $this->engine;
+  }
+
   /**
    * @return string
    */
@@ -13,4 +24,17 @@
 
   abstract public function markupContent($content, array $argv);
 
+  protected function markupError($string) {
+    if ($this->getEngine()->isTextMode()) {
+      return '('.$string.')';
+    } else {
+      return phutil_tag(
+        'div',
+        array(
+          'class' => 'remarkup-interpreter-error',
+        ),
+        $string);
+    }
+  }
+
 }
Index: src/markup/engine/remarkup/blockrule/PhutilRemarkupEngineRemarkupInterpreterRule.php
===================================================================
--- src/markup/engine/remarkup/blockrule/PhutilRemarkupEngineRemarkupInterpreterRule.php
+++ src/markup/engine/remarkup/blockrule/PhutilRemarkupEngineRemarkupInterpreterRule.php
@@ -49,6 +49,10 @@
       ->setAncestorClass('PhutilRemarkupBlockInterpreter')
       ->loadObjects();
 
+    foreach ($interpreters as $interpreter) {
+      $interpreter->setEngine($this->getEngine());
+    }
+
     $lines[$first_key] = preg_replace(
       self::START_BLOCK_PATTERN,
       "",
@@ -73,13 +77,18 @@
       return $interpreters[$matches[1]]->markupContent($content, $argv);
     }
 
-    $message = sprintf('No interpreter found: %s', $matches[1]);
+    $message = pht('No interpreter found: %s', $matches[1]);
 
     if ($this->getEngine()->isTextMode()) {
       return '('.$message.')';
     }
 
-    return hsprintf('<div style="color: red;">%s</div>', $message);
+    return phutil_tag(
+      'div',
+      array(
+        'class' => 'remarkup-interpreter-error',
+      ),
+      $message);
   }
 
 }
Index: src/markup/engine/remarkup/blockrule/PhutilRemarkupEngineRemarkupTestInterpreterRule.php
===================================================================
--- src/markup/engine/remarkup/blockrule/PhutilRemarkupEngineRemarkupTestInterpreterRule.php
+++ src/markup/engine/remarkup/blockrule/PhutilRemarkupEngineRemarkupTestInterpreterRule.php
@@ -12,7 +12,7 @@
 
   public function markupContent($content, array $argv) {
     return sprintf(
-      "Content: %s\nArgv: %s",
+      "Content: (%s)\nArgv: (%s)",
       $content,
       http_build_query($argv));
   }