The "ignore user" link has been exposed and has been placed on the bottom right sidebar of the user profile page so people don't accidentally click on it. Here's how to ignore a user:
1. Click on the user's avatar image
2. Visit the user profile page
3. Click on the "Ignore user" link in the bottom right of your screen to add this user to your ignore list.
To manage ignore users:
1. Visit "My Profile"
2. Click on the "Settings" link
3. Click on the "Ignored Users" link
4. Add or delete ignored users from here