I solved that problem by putting a JavaScript bookmarklet in my browser that narrows page text. I found this online, but I forgot where; hopefully HN doesn't mangle the following text... (you'll need to remove linebreaks to get it to work)

    javascript:(function(){var%20newSS,%20styles='body%20{%20margin-left:
    auto;%20margin-right:auto;%20max-width:45em;}';if(document.createStyleSheet
    )%20{document.createStyleSheet(%22javascript:'%22+styles+%22'%22);%20}%20
    else%20{%20newSS=document.createElement('link');%20newSS.rel='stylesheet';%20
    newSS.href='data:text/css,'+escape(styles);%20document.getElementsByTagName
    (%22head%22)[0].appendChild(newSS);%20}%20})();