This is absolutely a necessity in the friendly battle part of the game! If we can communicate with our friends we can discuss the battle we just had and we can find out what our friends are doing at the moment to see if they are busy or ready for a fight and make the challenge button within the message part!
This will eliminate the constant challenge decline challenge decline loop you end up in! If you are IM with a friend you know you will both be ready to fight!
In an earlier thread I said chat in battles would not be good but that was because in regular battles you are rushing to collect stuff and move on to other battles ASAP and also people could become abusive if they lost!
Friendly is different nothing to win or lose and you can always remove a friend if they become abusive!