You can also select two additional options when allowing discussion likes.
Only graders can like [1]: select this checkbox if you want to limit the liking functionality to only graders in the course, which means only users with the Edit Grades permission can see the Like link. However, all users will still see the total number of likes for each reply.
Sort by likes [2]: select this checkbox if you want the discussion to sort replies by the number of likes. Sorting cannot be changed by any users unless you remove the sorting setting. This option may take at least 10 seconds to cache the page and view sorting appropriately.
Discussion replies are sorted in descending order. In threaded discussions, replies retain the associated parent. For example, a new discussion may receive two replies. Then, Reply 1 gets individual replies a, b, and c, and Reply 2 gets individual reply d. If Reply 2 itself is liked, and reply b is liked, the discussion threads will be sorted first with Reply 2 (and reply d), then Reply 1 with reordered replies of b, a, and c.