Communication is about sending and receiving messages containing consciousness objects, but this does not mean that messages fully correspond to the conscious objects of the sender or the receiver or that the sender and receivers conscious objects are fully the same.
This is because messages might fail to fully capture the consciousness objects in two ways:
The message might fail to capture the intended consciousness objects according to the sender. It could be a bad articulation, using the wrong words, wrong body-language, the wrong order, context or texture.
The message might fail to capture the consciousness objects according to the receiver. The conscious objects created in the receiver while interpreting the message could differ from the senders intended consciousness objects.
So if symbols and letters could be errors and typos how are humans able to comprehend each other?
Luckily humans are not computers and communication between agents is improving its own process over time in three ways:
The sender is getting better at creating messages, the messages are corresponding more and more clearly to the senders intended consciousness objects.
The receiver is getting better at receiving messages, the conscious objects interpreted from messages are corresponding more and more to the senders intended consciousness objects.
The sender and receiver are improving their interpersonal hermeneutics which makes them better at communicating with each other. The sender is getting better at creating messages for the receiver and the receiver is getting better at understanding messages from the sender.
Since there is a relationship between messages and consciousness, communication cannot be reduced to it's extramental contents without losing some part of meaning because it is dependent on interpersonal or intersubjective hermeneutics which is an innate human ability.
This theory of communication should be compatible with all forms of communication including mathematical formulas, poems, music, literature, non-verbal, verbal, movies, art, paintings, programming, science, journalism.