Template hook for Discourse Plugin "Join Discussion Link" section?

Hi Angus,

The use case is for the same website as

so there’s private Discourse comments alongside the public Wordpress comments on a site using a classic theme. I’d like to be able to add a heading and some text explanation above the Join Discussion Link for context/user experience. I’m able to fake it visually with a theme-default widget area that comes after the post entry and a bunch of CSS, but it’s not ideal document structure-wise (in this case the widget gets picked up as part of the article in reader view/mode, while the actual .wpdc-join-discussion div doesn’t). I could create a new widget area that sits outside the article layer, but this customization logically belongs inside the .wpdc-join-discussion div along with the Join Discussion Link.