I forgot to mention, your update did fix the issue! Thank you.
For anyone else running into this issue while running WP-Rocket with WP-Discourse. The following code (insert in your Wordpress function file) will ensure once a comment is made on the corresponding Discourse post, it will purge the cache for that post.
if( function_exists( 'rocket_clean_post' ) ){
add_action( 'wpdc_after_webhook_post_update', 'bulk_rocket_clean_post’);
}
function bulk_rocket_clean_post(array $ids){
foreach ($ids as $id) {
rocket_clean_post($id);
}
}