How can I add/remove a user from the "favourites" list?

How can I add/remove a user from the "favourites" list?

In a user's profile next to his/her name you will find a star icon; by clicking on it you will mark that user as "Favourite". The star will light up to show that your preference has been saved. To remove a user from the list of favourites, simply click on the star icon again; once it is turned off, the user has been removed from the favourites.