I agree, I don't understand why "to him" is not acceptable. Perhaps there is some language nuance (direct vs. indirect objects) that I'm missing, but I found some examples from french.about.com, and it uses "to him/her":
I'm talking to him. Je lui parle.
I am surprised: here I expected to be marked wrong...because I wrote... I read a journal "to" him...no this time Duo accepted ... whereby the very same grammar construction in English had been marked wrong in the correction. in the previous exercise two minutes ago. I just thought: I read him a journal is not as good English as I read a journal to him... this time... wow... I can continue!!!!!!!!!!!!!!!!!