Description:
When someone replies to a comment I make in a thred. Just like the LIKE button, have an AKNOWLEDGE button to signal that the person who was replied to, acknowledge/agrees/okays the comment.
This button should only be available if a comment is replied to him.
Example
Peter posts a message or a new thread.
John replies to Peter with a comment.
Peter acknowledges the comment from John by pressing a button.
John now knows by a notification if enabled and a sign or icon in the post that Peter Okayed/agrees or Acknowledges the message.
Just like this, it can be enabled or used when someone is mentioned in the post with the @ sign.