Hey @Full30,
Posts are published using the user’s Discourse account if their Discourse username is filled in their Wordpress profile.
If you’re using DiscourseConnect with WP Discourse and have the “Update Userdata” Webhook enabled this will happen automatically.
If a user does not have a Discourse username in their Wordpress profile the “Publishing Username” in the Connection settings will be used, which is what happened with that post you linked (you have system as the publishing username).