From what I understand the comments are in a MySQL database table on the Wordpress host's server.
A podcast app would then just have to access that database and can implement the UI for comments how they like.
@dave @adam Does it need to be federated? Commenters on Wordpress can interact and the comments are pinned to the post... sticky just like YouTube. When someone is listening to a podcast and an app has a front end to the comment database anyone can comment just like people do on blogs brought a browser.
Intended for all stake holders of podcasting who are interested in improving the eco system