Undefined index: comment_node_article_form in drupal_retrieve_form()

Never mind... This was due to the Node Processor settings set to Article and not Node. I will close and mark as such.

The issue was resolved by overriding the node feeds importer on the admin page: administration page. Structure -> Feeds Importers

In case anyone else runs into this, the error was as follows:

• Notice: Undefined index: comment_node_article_form in drupal_retrieve_form() (line 760 of /path-to-my-site/includes/form.inc).
• Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'comment_node_article_form' was given in drupal_retrieve_form() (line 795 of /path-to-my-site/includes/form.inc).

Andrew