I have been lurking a bit since near the beginning, and finally signed up specifically to post thanks for setting the site to make some use the full browser window. It’s very unfashionable, but everyone else is wrong. We need more of this - why is the text of posts forced to wrap? It uses well under half my browser window width.
If you don’t like the width, can’t you just size your browser window to whatever width you like? With sites that artificially pad the sides with whitespace, there’s no simple or consistent way for someone with a wide monitor to force the content on a page to use the available space. Windows even has easy keyboard shortcuts for popping windows to half screen widths.