I figure that its about the person's values. To some people, a nice comment from someone makes their whole entire day, and they are bouncing around for weeks. For others, they realise that this comment has been thrown around like hotcakes to everyone within a 5 mile radius, thus it is an empty and meaningless comment and therefore is unnecessary. It depends on the person really.

I find those sorts of comments to be redundant. Unless the comment somehow fixes or has some sort of effect on the issue at hand, then they are not necessary. Just like any other "technique" the therapist has... if it is not of any use then stop using it. I wish that a comment like "that must have really hurt" and nothing but a bit of empathy could have some kind of positive effect on my mental illness. But unfortunately they are more complicated than that !!