Comment liking is a great way to encourage positive feedback amongst teams. Liking can also be used in the place of quick comments (e.g. “I agree!”, “Sounds good”, “+1”, etc), allowing people to weigh in on tasks without subscribing for notiﬁcations.
You can like any comment by clicking the "Like" link appended to the comment (including attachment-only comments) beside the comment's date/timestamp.
“Liking” a comment changes the blue "Like" link to a thumbs-up icon, greying it out but still allowing it to be clicked to undo.
“Likes” and like counts are marked with a small thumbs up icon and the name of the person who has liked the comment.
While "Likes" are not displayed in the task activity feed, in-app notifications will still be displayed to the comment author. Notifications for "Un-likes" are not displayed.
"Like" notifications are also displayed in the Notifications Popover, so if someone likes one of your comments while you’re away from your desk, you’ll still be able to view the notification there.
Email notifications are also sent for comment likes, but do not quote the liked comment so as to avoid confusion with comment notification emails.
Liking on the mobile site is essentially the same as on the web app. The blue “Like” link will appear under each comment, display a grey thumbs-up icon along with the number of likes for that comment, and tapping the counter will take you to a page with a list of the users who have liked the comment.