diff --git a/src/js/_enqueues/vendor/tinymce/plugins/wordpress/plugin.js b/src/js/_enqueues/vendor/tinymce/plugins/wordpress/plugin.js
index 2f9283281f..fdb3856d78 100644
--- a/src/js/_enqueues/vendor/tinymce/plugins/wordpress/plugin.js
+++ b/src/js/_enqueues/vendor/tinymce/plugins/wordpress/plugin.js
@@ -113,8 +113,13 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 						'alt="" title="' + title + '" data-mce-resize="false" data-mce-placeholder="1" />' );
 			}
 
-			if ( event.load && event.format !== 'raw' && hasWpautop ) {
-				event.content = wp.editor.autop( event.content );
+			if ( event.load && event.format !== 'raw' ) {
+				if ( hasWpautop ) {
+					event.content = wp.editor.autop( event.content );
+				} else {
+					// Prevent creation of paragraphs out of multiple HTML comments.
+					event.content = event.content.replace( /-->\s+<!--/g, '--><!--' );
+				}
 			}
 
 			if ( event.content.indexOf( '<script' ) !== -1 || event.content.indexOf( '<style' ) !== -1 ) {
@@ -608,6 +613,9 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 
 		if ( hasWpautop ) {
 			event.content = wp.editor.removep( event.content );
+		} else {
+			// Restore formatting of block boundaries.
+			event.content = event.content.replace( /-->\s*<!-- wp:/g, '-->\n\n<!-- wp:' );
 		}
 	});