Attention all, I have resolved the issue, and some may find the following information useful for future reference.
As mentioned above, some themes automatically list the author's name with each post. Additionally, some themes go one or two steps further by including the author's avatar next to their name, or by making the author's clickable (which takes you to a page of their posts)
The following is a list of WordPress.com blog themes that automatically list the author with each post:
"[A]" indicates that the author's avatar is also shown.
"[C]" indicates that the author's name is clickable, taking you to a page of their posts.
Digg 3 Column
Fleur De Lys
P2 [C] [A]
Prologue [C] [A]
Redoable Lite [C]
Shocking Blue Green
Silver is the New Black
The Journalist v1.3