You can also fold the article with 'd', and show the top comment with 'c'. Shift+C opens the comment thread too. Pressing '?' will bring up a box that lists all the shortcuts:

   j or →    Select next article
   k or ←    Select previous article
   c         Toggle Hacker News top comment
   shift + c Open Hacker News comments page in a new window
   d         Toggle article content
   enter     Follow the article link in this window
   shift + enter Follow the article link in a new window
   ?         Show this keyboard shortcuts dialog