Recently in a seminar I had a participant who gave me excellent nonverbal feedback. She had a perpetual genuine smile and asked a couple of excellent, thought-provoking questions which initiated good seminar discussion.
At a break I complimented her on this trait. Her response was intriguing. She said that she always wanted to raise the bar of interaction when listening to a speaker or a moderator at a meeting. She wanted to make sure there was a connection with the talker that made both the speaker and the listener work harder at exchanging ideas. She thought she could make the speaker even better with aggressive positive nonverbal reactions. She was very conscious of making that happen—thus the overt feedback.
I've thought about that comment. You the listener can make the speaker more effective by "raising the bar" during the communication act by the way you respond. When you make such a conscious effort to contribute even when you are not to speak, you pay better attention and encourage the speaker even more to give his or her best in that presentation.
Listening is not passive; you can be very actively involved in communicating, even when you don't speak. As Charles Dickens said, “Electric communication will never be a substitute for the face of someone who with their soul encourages another person to be brave and true.”