Facebook's expanded their @Mentions capabilities, allowing users to tag people, events or fan pages in their comments now. Previously, this ability was restricted to status updates and wall posts, but now users can place a "@" in their comments, followed by the name of the person, event or fan page they want to tag, selecting their name from the drop down menu that appears and it then notifies the user, event or page tagged.
Now possible in comments
Also new, Facebook's allowed those using "Facebook as a page" to publish comments that mention themselves on posts of other pages, thereby linking users back to their page. In other words, Facebook comments don't often allow URL posts, however, this is a way to get around that feature and also advertising your own page in the process.