Earlier quoted context omitted.
> Wouldn't that make you think that we should revisit the sidebar No. The sidebar works and is effective when there's significant horizontal space, such as on a desktop screen with ample horizontal space. It just does not work when horizontal space is a premium, as is the case on smartphones (which generally barely fit a standard typographic line length at readable size in portrait)
Sidebars don't add anything necessary to the user experience. It's just clutter. If there's enough horizontal space, I suggest using columns instead, they fit the purpose better.
This is a really weird argument; sidebars are preferable to a lot of other patterns depending on the site and doesn't at all mean the content is less important than anything else on the page.