Amanda, I’m writing this as a reply to you within the admin UI of my WordPress comments dashboard (at /wp-admin/edit-comments.php). I’ve tried this out a couple of times and it seems to work incredibly well so far. I’ve written up more of the details on my site here: Threaded Replies and Comments with Webmentions in WordPress (http://boffosocko.com/2017/12/15/threaded-replies-with-webmentions-in-wordpress/). Hopefully you like it and find it as incredibly useful as I do.