Group Messaging

I'm a little confused about the group messaging feature. I understand that it's set up like a chat room so that all recipents can see and respond the message, but when I get a group message from someone else, I don't always see who it's from (just says Group MMS at the top) and I would like to know who I'm responding to and also that when I do respond, it only goes to the sender.

Also, I've turned off group messaging in preferences in the settings just to test it out and I can still do group messages.

All of the confusion!