Firstly, tap the smiley-face, star, or lock icon to the top right of the moment you want to delete a comment from. Tap Comment in the bottom right of the box that appears.
iOS: Delete the comment by swiping it to the left. Tap the red Delete button that appears.
Android: Delete the comment by pressing and holding on it until a confirmation dialog appears. Tap Yes to confirm.
Windows Phone 8: Delete the comment by pressing and holding on it until a red Delete button appears. Tap it to confirm.