Sorry if this topic already exists, I am rather new (or returning from a long hiatus prior to which I was very new) to the forums, and couldn't find this.
I would love an option to be able to reply all to messages that have multiple characters in them. I ran into this issue the other day. I received a message from someone and the message was to myself and three other players. To reply all I had to start a brand new message and include those other three in my response, a reply all option would save time and be more convenient I think.
