First of all, this isn’t correct. Try viewing as an anonymous user. There are also special rules for new users where they are heavily sandboxed. (If you are talking about established users who have been on the site for 3+ years and posted many times, that’s different.)
Second, I would like to bring your attention to the following lines in robots.txt which is default for all Discourse instances:
Disallow: /users/
Disallow: /u/