Hate to be picky but it kind of depends on the comment. A fav is, in some respects, a manner of commentary and actually can communicate more than "this is great" or because it implies that the reviewer would want to see the art again sometime. If someone's planning on leaving a novella about how they feel about a piece, well then you can keep the fav. Actually, I'd like the option of having a face to face conversation about a piece and art, philosophy and life in general. Can I vote for that?