Sort by: Recently "Commented" VS Recently "Created"

Will sorting threads by recently "commented" include posts that were recently "created" but don't yet have any replies/comments? Or… do you have to sort by recently "created" to see new posts that don't yet have any replies/comments?

In the old forum, posts would be highlighted in bold whether they were new posts created since a person's last visit to the forums, or old posts with new comments posted since a person's last visit to the forums. Made it easy to see a glance all new activity, whether a new post or new comment on an old post.