The section separator element is a very nice feature but unless you create a series of them as a global element (recommended), any design changes require a page-by-page audit if changes are needed to the color or other settings. If you want more control and fewer DOM elements, using CSS is an alternative, especially when working with the title elements. The bonus is that you can still use most of the element features without a problem.
When it comes to CSS, you have to remember that many HTML elements are block-level and act like a box. These boxes spread the width of the parent container and stack on top of each other. The heading tags (h1-h6) are a block-level element use display:block by default. This is the key to creating CSS based dividers. As you can see by adding some basic CSS you can see your block.