It's for taking notes.
Just jot something down in the margins to help you remember key ideas. Your monitor may get a little cluttered, and the notes don't scroll with the posts, but eventually you will be able to get everything all lined up again.
I like Scott's answer better but the real answer is this is a styling guide mandate from my colleagues in Siemens Corporate. Unfortuantely, we must live with that for a while.
Since this post better belongs in the Community Suggestions area, I am going to move it there.