Articles appearing on main pg of IF, does have dislike button. After reading article either one likes or dislikes. Writer of the article doesnt reply on comments.
Whereas forum articles are open for discussions within forum rule frame. Views are shared, debated on by members. Reason is explained at times about a view. Which is beyond like & dislike. Different topics are opened to express one's thought. A healthy atmosphere invites different perspectives. So all platforms are different having different set of rules & requirements. May be dislike button is not much needed in a forum because people are free to share their views instead of just liking or not liking.