Think about all the time people save by replying "This!" instead of "I agree with what you are saying." Plus it contributes nothing and minimizes comeradery between the commenter and the "this" reply-guy.
Your words struck a chord with me, and I find myself nodding in agreement. I wholeheartedly agree with everything you've said. It's refreshing to hear such a clear and well-articulated take on "this". I couldn't have said it better myself.