Dear Ms. Baym,
Chapter 3 of your book explains very well in detail what mediated communication is and how different it is in comparison with face-to-face. Face to face communication requires less thinking when it comes to figuring out a reaction because like you said, we can tell by social cues. Quoted from your book, "Social presence is a psychological phenomenon regarding how interactants perceive one another, not a feature of a medium. However, the perception of social presence was attributed to the nonverbal cues enabled or disabled by mediation. Important nonverbal cues include facial expression, direction of gaze, posture, dress, physical appearance, proximity, and bodily orientation" (Baym 52). Without social presence, communication in digital space requires more effort to maintain a strong communication between two people. People use social cues in order to make communication synchronous rather than asynchronous. I agree with the answers of the survey you mentioned in the beginning of the chapter that face-to-face communication is a lot richer than talking through the phone because you can experience all the social cues and will be clear of everything rather than being confused of the other person's message.
As for communication in digital spaces, you mentioned Media Richness Theory which is defined as, "a medium's richness as its information-carrying capacity, which they based on four criteria which is the speed of feedback, the ability to communicate multiple cues, its use of natural language rather than numbers, and its ability to readily convey feelings and emotions" (Baym 53). The Media Richness Theory recognizes which media could be used to replace social cues, I believe. The richer the media, the more beneficial it will be for communication.
I found this chapter to be easy to read because it was interesting to learn about how certain preferences to communicate affects a message.