diff --git a/includes/OutputTransform/Stages/DeduplicateStyles.php b/includes/OutputTransform/Stages/DeduplicateStyles.php
index 22a0f9ce428..b46208d24d1 100644
--- a/includes/OutputTransform/Stages/DeduplicateStyles.php
+++ b/includes/OutputTransform/Stages/DeduplicateStyles.php
@@ -2,11 +2,12 @@
 
 namespace Mediawiki\OutputTransform\Stages;
 
-use MediaWiki\Html\Html;
+use MediaWiki\Html\HtmlHelper;
 use Mediawiki\OutputTransform\ContentTextTransformStage;
 use MediaWiki\Parser\ParserOutput;
-use MediaWiki\Parser\Sanitizer;
 use ParserOptions;
+use Wikimedia\RemexHtml\Serializer\SerializerNode;
+use Wikimedia\RemexHtml\Tokenizer\PlainAttributes;
 
 /**
  * Generates a list of unique style links
@@ -20,28 +21,32 @@ class DeduplicateStyles extends ContentTextTransformStage {
 
 	protected function transformText( string $text, ParserOutput $po, ?ParserOptions $popts, array &$options ): string {
 		$seen = [];
-		return preg_replace_callback( '#<style\s+([^>]*data-mw-deduplicate\s*=[\'"][^>]*)>.*?</style>#s',
-			static function ( $m ) use ( &$seen ) {
-				$attr = Sanitizer::decodeTagAttributes( $m[1] );
-				if ( !isset( $attr['data-mw-deduplicate'] ) ) {
-					return $m[0];
-				}
-
-				$key = $attr['data-mw-deduplicate'];
+		return HtmlHelper::modifyElements(
+			$text,
+			static function ( SerializerNode $node ): bool {
+				return $node->name === 'style' &&
+					( $node->attrs['data-mw-deduplicate'] ?? '' ) !== '';
+			},
+			static function ( SerializerNode $node ) use ( &$seen ): SerializerNode {
+				$key = $node->attrs['data-mw-deduplicate'];
 				if ( !isset( $seen[$key] ) ) {
 					$seen[$key] = true;
-
-					return $m[0];
+					return $node;
 				}
-
 				// We were going to use an empty <style> here, but there
 				// was concern that would be too much overhead for browsers.
 				// So let's hope a <link> with a non-standard rel and href isn't
 				// going to be misinterpreted or mangled by any subsequent processing.
-				return Html::element( 'link', [
+				$node->name = 'link';
+				$node->attrs = new PlainAttributes( [
 					'rel' => 'mw-deduplicated-inline-style',
 					'href' => "mw-data:" . wfUrlencode( $key ),
 				] );
-			}, $text );
+				$node->children = [];
+				$node->void = true;
+				return $node;
+			},
+			$options['isParsoidContent'] ?? false
+		);
 	}
 }
diff --git a/includes/language/Message.php b/includes/language/Message.php
index 921a7797cce..5409d5cd3ed 100644
--- a/includes/language/Message.php
+++ b/includes/language/Message.php
@@ -1447,6 +1447,12 @@ class Message implements MessageSpecifier, Serializable {
 				// they're inside they already are from the outer div.
 				'unwrap' => true,
 				'userLang' => $this->getLanguage(),
+				// Although we *could* have template styles in messages,
+				// they are rare enough that it's not worth the performance
+				// hit on all messages to run deduplication (and the
+				// deduplication would only extend within the message anyway,
+				// not to the article content)
+				'deduplicateStyles' => false,
 			] )
 			: $out;
 	}
diff --git a/tests/parser/ParserTestRunner.php b/tests/parser/ParserTestRunner.php
index 47c1e0f6321..69223980f16 100644
--- a/tests/parser/ParserTestRunner.php
+++ b/tests/parser/ParserTestRunner.php
@@ -1456,6 +1456,7 @@ class ParserTestRunner {
 					'allowTOC' => !isset( $opts['notoc'] ),
 					'unwrap' => !isset( $opts['wrap'] ),
 					'skin' => $this->getSkin( $opts['skin'] ?? 'fallback' ),
+					'deduplicateStyles' => isset( $opts['deduplicateStyles'] ),
 				] );
 				$out = preg_replace( '/\s+$/', '', $out );
 			}
diff --git a/tests/parser/parserTests.txt b/tests/parser/parserTests.txt
index 430a859b989..9e042b45df1 100644
--- a/tests/parser/parserTests.txt
+++ b/tests/parser/parserTests.txt
@@ -46,6 +46,7 @@ version=2
 # thumbsize=NNN set the default thumb size to NNNpx for this test
 # wrap          include the normal wrapper <div class="mw-parser-output"> (since 1.30)
 # local         format section links in edit comment text as local links
+# deduplicateStyles apply style deduplication to the output
 #
 # Configuration globals:
 #
diff --git a/tests/phpunit/includes/OutputTransform/Stages/DeduplicateStylesTest.php b/tests/phpunit/includes/OutputTransform/Stages/DeduplicateStylesTest.php
index 3ce561ed50c..bf8a1258d55 100644
--- a/tests/phpunit/includes/OutputTransform/Stages/DeduplicateStylesTest.php
+++ b/tests/phpunit/includes/OutputTransform/Stages/DeduplicateStylesTest.php
@@ -33,12 +33,12 @@ class DeduplicateStylesTest extends OutputTransformStageTest {
 		$dedup = <<<EOF
 <p>This is a test document.</p>
 <style data-mw-deduplicate="duplicate1">.Duplicate1 {}</style>
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1">
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1" />
 <style data-mw-deduplicate="duplicate2">.Duplicate2 {}</style>
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1">
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate2">
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1" />
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate2" />
 <style data-mw-not-deduplicate="duplicate1">.Duplicate1 {}</style>
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1">
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1" />
 <style data-mw-deduplicate="duplicate3">.Duplicate1 {}</style>
 <style>.Duplicate1 {}</style>
 EOF;
diff --git a/tests/phpunit/includes/content/JsonContentHandlerIntegrationTest.php b/tests/phpunit/includes/content/JsonContentHandlerIntegrationTest.php
index 9b91214e172..7955ced731f 100644
--- a/tests/phpunit/includes/content/JsonContentHandlerIntegrationTest.php
+++ b/tests/phpunit/includes/content/JsonContentHandlerIntegrationTest.php
@@ -75,7 +75,9 @@ class JsonContentHandlerIntegrationTest extends MediaWikiLangTestCase {
 			true
 		);
 		$this->assertInstanceOf( ParserOutput::class, $parserOutput );
-		$this->assertEquals( $expected, $parserOutput->getText() );
+		$this->assertEquals( $expected, $parserOutput->getText( [
+			'deduplicateStyles' => false,
+		] ) );
 	}
 
 	/**
diff --git a/tests/phpunit/includes/content/TextContentHandlerIntegrationTest.php b/tests/phpunit/includes/content/TextContentHandlerIntegrationTest.php
index 8d13f4b3a6f..230ff215d11 100644
--- a/tests/phpunit/includes/content/TextContentHandlerIntegrationTest.php
+++ b/tests/phpunit/includes/content/TextContentHandlerIntegrationTest.php
@@ -38,7 +38,9 @@ class TextContentHandlerIntegrationTest extends MediaWikiLangTestCase {
 		$contentRenderer = $this->getServiceContainer()->getContentRenderer();
 		$po = $contentRenderer->getParserOutput( $content, $title, null, $parserOptions );
 
-		$html = $po->getText();
+		$html = $po->getText( [
+			'deduplicateStyles' => false,
+		] );
 		$html = preg_replace( '#<!--.*?-->#sm', '', $html ); // strip comments
 
 		if ( $expectedHtml !== null ) {
diff --git a/tests/phpunit/includes/page/WikiPageDbTest.php b/tests/phpunit/includes/page/WikiPageDbTest.php
index 591d0a3fff9..a1f760f2827 100644
--- a/tests/phpunit/includes/page/WikiPageDbTest.php
+++ b/tests/phpunit/includes/page/WikiPageDbTest.php
@@ -937,7 +937,9 @@ class WikiPageDbTest extends MediaWikiLangTestCase {
 
 		$opt = $page->makeParserOptions( 'canonical' );
 		$po = $page->getParserOutput( $opt );
-		$text = $po->getText();
+		$text = $po->getText( [
+			'deduplicateStyles' => false,
+		] );
 
 		$text = trim( preg_replace( '/<!--.*?-->/sm', '', $text ) ); # strip injected comments
 		$text = preg_replace( '!\s*(</p>|</div>)!m', '\1', $text ); # don't let tidy confuse us
diff --git a/tests/phpunit/includes/parser/ParserOutputTest.php b/tests/phpunit/includes/parser/ParserOutputTest.php
index a4ef882a99e..6469af5f5bd 100644
--- a/tests/phpunit/includes/parser/ParserOutputTest.php
+++ b/tests/phpunit/includes/parser/ParserOutputTest.php
@@ -449,12 +449,12 @@ EOF
 				[], $dedupText, <<<EOF
 <p>This is a test document.</p>
 <style data-mw-deduplicate="duplicate1">.Duplicate1 {}</style>
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1">
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1" />
 <style data-mw-deduplicate="duplicate2">.Duplicate2 {}</style>
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1">
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate2">
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1" />
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate2" />
 <style data-mw-not-deduplicate="duplicate1">.Duplicate1 {}</style>
-<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1">
+<link rel="mw-deduplicated-inline-style" href="mw-data:duplicate1" />
 <style data-mw-deduplicate="duplicate3">.Duplicate1 {}</style>
 <style>.Duplicate1 {}</style>
 EOF