Aw thanks!
You’ve already discovered the Discourse/WP plugin – I’ll just note that while the project page lists blog.discourse.org and BoingBoing.net as examples, BoingBoing has unfortunately moved to a monetized newsletter format – and IIRC they weren’t embedding replies anyway.
It looks like the plugin setup may be a bit challenging but it must be doable.
Whatever you decide, I look forward to seeing how your project goes!