Yo dawg, I heard you like comments...
Facebook is currently testing a redesign of its commenting system for Page posts that will allow users to reply to specific comments and will also sort them based on an algorithm.
Some pages are now seeing threaded comments under their posts, which give users the ability to create their own little mini-conversations within the larger conversation happening in the entire comments thread. The new format shows a "write a reply" option under specific comments.
Inside Facebook obtained this screencap of the new commenting system:
The new commenting structure also brings a new organizational algorithm to page posts, as Facebook is testing an algorithm that throws the most engaging comments to the top of the thread (whichever ones have the most likes and replies).
Of course, this test brings Facebook comments a little closer to how they appear in the third-party plugin. Facebook-enabled comments on other sites have had threaded comments for some time now, and they are ranked based on the commenters' relationship (your friends' comments rise to the top).
Facebook confirmed that the new threaded comments are only being tested on Pages, not posts from individual profiles. I say that comment threads are a long time coming, as it's incredibly difficult to wade through hundreds of comments in posts from pages with a good number of fans. In theory, allowing comment replies will allow for more coherent discussion of posts and the new ranking algorithm will make sure the most interesting comments are seen by the largest number of people.