Facebook are set to be testing a new comment system for a small amount of users in a series of design updates to be more Messenger alike, turning it into a conversation type messages like other social apps done.
This news first reported on BuzzFeed as Facebook explains:
We are always working to make Facebook a more visual and engaging place to have conversations. So we’re testing multiple design updates in News Feed, including a more conversational way to comment on posts
The design changes will be part of a new design changes that Facebook are currently testing, including adding it’s Reactions feature into Messenger.