Hi Nick. 
The WP-Discourse plugin is designed to override those comments and replace them with replies from your Discourse instance. Since Discourse requires a login to use, you will have to choose if you want to use Discourse for discussions, or allow anonymous commenting in WordPress. 
Notably, most users will only need to login into Discourse once, and that process is fairly simple. There are other benefits to engaging with users this way, but of course you will have to balance them with your goals.
I personally have not heard of this. Have you seen this elsewhere?
Discourse has related topics, of course. 