Yeah, there is an overlap. We're calling it cross-app comments, and it's using the socialInteract RSS tag.
Podverse has them in their app. https://podverse.fm/episode/dTWX_aqL- Click on the comments, and you'll see this.
Same thing with the Podcast Index page.
https://podcastindex.org/podcast/920666
Everything there is from AP.
One issue apps are having is how to make it easy to post comments from within the app. The displaying comments has been solved, but next is in-app replies to comments.