Earlier quoted context omitted.
If only it was simple to configure my user agent to act as my agent and format things readably. I prefer moderate line widths. Even at half-screen on my 29" widescreen monitor, unformatted text is too wide.
Yes, this would be the best. Web site provides the content and the browser (user agent) decides how best to render it, potentially different than how the web developer would want it.
Remember when browsers supported user styles out of the box and put them in a somewhat discoverable location?