UPDATED WITH COMMENT FROM FACEBOOK
Facebook appears to be rolling out its reply to comment feature site wide, allowing users to start threaded comments on personal profiles' posts.
For two years, this feature has only been available for pages with 10,000+ likes.
The option to reply to comments only appears on statuses and photos posted directly to Facebook. Cross-posted content, like photos from Instagram, do not currently give users the option to reply directly to comments.
Facebook first introduced replies in March of 2013, and since then it's only been available to pages.
"This will make it easier for you to interact directly with individual readers and keep relevant conversations connected. Also, the most active and engaging conversations among your readers will be surfaced at the top of your posts ensuring that people who visit your Page will see the best conversations," said Facebook at the time.
I've not seen any evidence that Facebook is reordering comments on personal posts – but the reply button is definitely present on posts from users. I've reached out to Facebook for confirmation on the rollout and will update this article accordingly.
So long, @tagging and ^^.
UPDATE: Facebook confirmed the test.
"We are testing the ability to reply directly to specific comments on a post so people can navigate comments more easily and have deeper conversations.” a spokesperson tells me.