Yes, you need 50 reputation. See the "What is reputation?" section in the [faq](http://unix.stackexchange.com/faq), and the [How does the comment system and comments work?](http://meta.stackoverflow.com/questions/19756/how-does-the-comment-system-and-comments-work/19757#19757) entry on the main meta

You can always comment on your own questions and answers, however, so you should see the link on this question:

![Screenshot of the add comment link](http://mrozekma.com/so-unix-add-comment.png)