Index: wp-includes/comment.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/wp-includes/comment.php b/wp-includes/comment.php
--- a/wp-includes/comment.php	
+++ b/wp-includes/comment.php	(date 1668434022286)
@@ -3621,6 +3621,20 @@
 		'user_id'
 	);
 
+	/**
+	 * Allows a custom validation.
+	 *
+	 * @since TBD
+	 *
+	 * @param null|WP_Error $custom_validation Your possible custom error.
+	 * @param array         $commentdata       Array of comment data to be sent to wp_insert_comment().
+	 * @param array         $comment_data      The raw comment data from the function call.
+	 */
+	$custom_validation = apply_filters( 'comment_form_fields_validation', null, $commentdata, $comment_data );
+	if ( is_wp_error( $custom_validation ) ) {
+		return $custom_validation;
+	}
+
 	/**
 	 * Filters whether an empty comment should be allowed.
 	 *