diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_node.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_node.yml
index 9681fbb..07d37ce 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_node.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_node.yml
@@ -14,7 +14,10 @@ process:
     default_value: "und"
   title: title
   uid: node_uid
-# migrate_drupal keeps numeric entity ids. If it wouldn't then:
+# Core migrations are designed for replacing the upgrade path and therefore
+# all node and user ids are preserved. For that reason we do not need to look-up
+# the user id for the node. If you're writing a custom migration, user ids will
+# vary from the source site and a lookup as shown below will be required.
 #    plugin: migration
 #    migration: d6_user
 #    source: node_uid