A few weeks back Facebook added reactions to Messenger, and now they’ve extended it to comments too. So that you can “wow” and “sad” not just the posts and messages but comments too.
I think this will make comments too complicated. But, Facebook says “We’ve heard from people they’d like more ways to show their reaction in conversations on Facebook,” Unlike the implementation on posts and Messenger, the emoji seem to crowd and overlap a bit especially as more reactions are added. By the way, this feature will reduce the replies for a comment.
For reacting to a comment just hover over the Like button of that comment and see your default options of six. So, next time you see a hilarious comment use the reaction feature instead of replying to it.