The down vote button currently appears for some users on iOS. Twitter officially said it's not a dislike button (but it kind of is). Downvotes won't be public and won't change the order of replies. Upvotes will be shown as likes. Twitter is testing different designs for this, including upvote and downvote buttons, likes and dislikes, and the classic heart along with a downvote, as seen in the image. Link
