diff --git a/includes/CommentModifier.php b/includes/CommentModifier.php
index 00f484d04..a5e833455 100644
--- a/includes/CommentModifier.php
+++ b/includes/CommentModifier.php
@@ -478,7 +478,7 @@ class CommentModifier {
 		// If the last node is empty, trim the signature to prevent leading whitespace triggering
 		// preformatted text (T269188, T276612)
 		if ( !$container->lastChild->firstChild ) {
-			$signature = trim( $signature );
+			$signature = ltrim( $signature, ' ' );
 		}
 		// Sign the last line
 		$container->lastChild->appendChild(
diff --git a/modules/modifier.js b/modules/modifier.js
index 84ff7bef9..d323b56e3 100644
--- a/modules/modifier.js
+++ b/modules/modifier.js
@@ -434,7 +434,7 @@ function appendSignature( container ) {
 	// If the last node is empty, trim the signature to prevent leading whitespace triggering
 	// preformatted text (T269188, T276612)
 	if ( !container.lastChild.firstChild ) {
-		signature = signature.trim();
+		signature = signature.replace( /^ +/, '' );
 	}
 	// Sign the last line
 	container.lastChild.appendChild(