I'm not sure if I understood this at all. Anno Un is an avatar of Akira Kuno that allows him to interact with others. Then, why didnt he use to talk with his mother, which, not being able to talk and interact with her, was the reason of all the trauma of his life?
1 Answer
In episode 23 of the anime ("A Story I Won't See Coming"), during Akira Kuno's flashback, he creates the pen name "Anno Un" in order to submit his manga and finds out he is able to communicate to others through a loophole in the rules. As long as it is done through his proxy he can draw manga for others! The manga he created even reaches his mother, who is in the hospital at the time.
In episode 24 ("To You, From Me") during Akira's flashback, he also reveals that he is able to manifest his drawings. This is shown when he first draws a toy car. Eventually he comes up with a design for Anno Un and brings him into reality. He realizes this is the way he can also speak to his mother, but alas:
"And in the end... I couldn't get the message to mom."
This is because
his mom sadly passed away around the same time.
I hope this helps answer your question!