In late March, Facebook launched a new commenting system for Pages that allows users to reply to comments. The new system is on an opt-in basis for now, and Facebook has a few API tips to keep in mind if you decide to take your Page into this new territory.
The first view organizes what Facebook calls "top level comments," or comments that are not replies. These comments can be ranked based "on the post and the number of top level comments on the post so far."
The second view is simply called "replies." Facebook says developers can access replies by "querying for the comments on a comment id."
The third, and final view, is the comment "stream." This is what you're most likely going to see the most of as it combines top level comments and replies into a single stream of data. The "stream" is also organized in chronological order so the newest comments are shown first.
If you've already been using the comments API, Facebook says that you should keep the following changes in mind:
If you need more information, check out the comments API documentation. If you want to start using the new API, you can opt in through the July 2013 Breaking Changes under the Advanced Tab of the app dashboard. On July 10, the new comments API will go into effect for everyone. Might as well get used to it now while it's still voluntary.