I think that's a configuration by Erel. Seems the new version of XenForo can support different kinds of presentations for different forums now. (The Share Your Creations is another such presentation, I'd imagine.)
For whatever it's worth, I dislike having the author on the bottom. Not only does it make the width of the lines overly long and waste space, I also actually like to know right away who wrote the post. In another thread Erel said it's more like a blog, which I disagree with. A blog is typically something a single person writes, which is identified by the blog header. This is a forum, where lots of people write, so I have no idea up front who wrote it.
Like I said, I dislike it. But I'll manage, I suppose. Not a hill I'm willing to die on, I accept that my opinions aren't perfectly aligned with those of Erel.