When emotions and feelings are shared between individuals, it is considered to be a part of spiritual communication. There is a sense of empathy that exists between individuals that we experience through the other forms of communication. You do not even have to have that person present in order for that sense to occur.
You hear phrases like "the spirit of the law"— which seem to say that it is the meaning behind the words… not the words themselves that matter. I believe that the spirit of the author is embedded in those words— even if the author has passed. How often do we find ourselves laughing or crying while watching an old movie, or reading a great book. It is this experience that proves spiritual communication exists.
Given that you can't point at an emotion or feeling and say "there, that's what I'm talking about"— it is very difficult to quantify spiritual communication. This lack of quantification is what makes spiritual communication so intangible in nature. I believe that spiritual communication is the glue that binds all forms of communication together. If we begin to understand this connection we will be able to better communicate what we "truly" mean in what ever form we choose to communicate with.