It looks like you may be using the Post Kinds plugin, so you should be able to reply to other sites using that and putting the requisite URL into the interface under "Post Properties" and including your response. The plugin will include the necessary u-in-reply-to microformat class and your webmention plugin will handle sending the response. If you'd like, you can try responding directly to this post at its permalink.
An alternate method is to use the Indieweb Press This bookmarklet for replies (if you're using the Indieweb Plugin) . You can find the bookmarklets at your /wp-admin/tools.php page about halfway down. Then you can click the bookmarklet on the page you'd like to reply to and it will craft a part of the post to send the reply and then you just add what you wanted to say before publishing to send the webmention.