diff --git a/src/wp-admin/includes/schema.php b/src/wp-admin/includes/schema.php
index 217d18d8275a0..9ef4078f89054 100644
--- a/src/wp-admin/includes/schema.php
+++ b/src/wp-admin/includes/schema.php
@@ -563,7 +563,6 @@ function populate_options( array $options = array() ) {
 
 		// 6.9.0
 		'wp_notes_notify'                 => 1,
-
 	);
 
 	// 3.3.0
diff --git a/src/wp-admin/options-discussion.php b/src/wp-admin/options-discussion.php
index 3b4e1ac3a2313..0c350475fe176 100644
--- a/src/wp-admin/options-discussion.php
+++ b/src/wp-admin/options-discussion.php
@@ -162,7 +162,7 @@
 <?php _e( 'A comment is held for moderation' ); ?> </label>
 <br />
 <label for="wp_notes_notify">
-<input name="wp_notes_notify" type="checkbox" id="wp_notes_notify" value="1" <?php checked( '1', get_option( 'wp_notes_notify' ) ); ?> />
+<input name="wp_notes_notify" type="checkbox" id="wp_notes_notify" value="1" <?php checked( '1', get_option( 'wp_notes_notify', 1 ) ); ?> />
 <?php _e( 'Anyone posts a note' ); ?> </label>
 
 </fieldset></td>
diff --git a/src/wp-includes/comment.php b/src/wp-includes/comment.php
index a6deb2db599f5..49c9c6b2cb966 100644
--- a/src/wp-includes/comment.php
+++ b/src/wp-includes/comment.php
@@ -2427,7 +2427,7 @@ function wp_new_comment_notify_postauthor( $comment_id ) {
 	$comment = get_comment( $comment_id );
 	$is_note = ( $comment && 'note' === $comment->comment_type );
 
-	$maybe_notify = $is_note ? get_option( 'wp_notes_notify' ) : get_option( 'comments_notify' );
+	$maybe_notify = $is_note ? get_option( 'wp_notes_notify', 1 ) : get_option( 'comments_notify' );
 
 	/**
 	 * Filters whether to send the post author new comment notification emails,
@@ -2458,6 +2458,19 @@ function wp_new_comment_notify_postauthor( $comment_id ) {
 	return wp_notify_postauthor( $comment_id );
 }
 
+/**
+ * Send a notification to the post author when a new note is added via the REST API.
+ *
+ * @since 6.9.0
+ *
+ * @param WP_Comment $comment The comment object.
+ */
+function wp_new_comment_via_rest_notify_postauthor( $comment ) {
+	if ( $comment instanceof WP_Comment && 'note' === $comment->comment_type ) {
+		wp_new_comment_notify_postauthor( (int) $comment->comment_ID );
+	}
+}
+
 /**
  * Sets the status of a comment.
  *
diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 58ee4053e0752..68dccd979f2fe 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -522,7 +522,7 @@
 // Email notifications.
 add_action( 'comment_post', 'wp_new_comment_notify_moderator' );
 add_action( 'comment_post', 'wp_new_comment_notify_postauthor' );
-add_action( 'rest_insert_comment', array( 'WP_REST_Comments_Controller', 'wp_new_comment_via_rest_notify_postauthor' ) );
+add_action( 'rest_insert_comment', 'wp_new_comment_via_rest_notify_postauthor' );
 add_action( 'after_password_reset', 'wp_password_change_notification' );
 add_action( 'register_new_user', 'wp_send_new_user_notifications' );
 add_action( 'edit_user_created_user', 'wp_send_new_user_notifications', 10, 2 );
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
index 0ef02aae4d0dc..7fe79b57c1b9b 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
@@ -36,18 +36,6 @@ public function __construct() {
 		$this->meta = new WP_REST_Comment_Meta_Fields();
 	}
 
-	/**
-	 * Send a notification to the post author when a new note is added via the REST API.
-	 *
-	 * @since 6.9.0
-	 *
-	 * @param WP_Comment $comment The comment object.
-	 */
-	public static function wp_new_comment_via_rest_notify_postauthor( $comment ) {
-		if ( 'note' === $comment->comment_type ) {
-			wp_new_comment_notify_postauthor( $comment->comment_ID );
-		}
-	}
 	/**
 	 * Registers the routes for comments.
 	 *