No professionally made webpage will have a line of text that goes from one edge of the screen to the other. You don't have to be a reading expert (or reading teacher, like me) to figure out that it's vastly more difficult to read long line lengths than short ones. You can read much faster with much less effort if you're reading something that is not more than 4-5" from side to side.
When I post an article, I always place at least 3 < blockquote > commands at the beginning of the article. That narrows the column to about the right width.