Yes, I understand what the difference between Reply and Reply All is, thanks.
The admin of this group has set it up so that its address always appears in the 'Reply To' field. In all other email clients that I know, hitting the Reply sends the reply to the group. There is nothing in the cc field, either received or sent. If I want to reply to the creator of the post, then I have to cut and paste the address. This is the normal behaviour for a Group: it's the way this group is set up, and the way that all other email clients behave, including, for example, Aquamail, on my Nexus. Yes it is possible to set up the group so that the default is to reply to the writer, but that is definitely not how this group is set up.
By the way, it would be good to see all the headers. If it is possible, could someone tell me how?
When I reply with Email on my Nexus, it sends the mail to the writer. If I send with Reply All, then it sends to the writer, and CCs to the group, so the writer receives a duplicate. Yes, I could just delete one address every time, but that is not how it should work. Something is wrong, and when something is wrong, I want to correct it as something more could go wrong.
I don't know how to view all the headers on Email. All I can see on the received message is the name of the sender at the top, then the sender's address, and then, in the To: field, it has the name (not the address) of the group. When I reply, it just has the writer's name in the To: field, and when I hit Reply All it also has the address of the group in the CC field, which is not how it should work at all. As I said, it is just Email that works this way. I've looked back at some old threads and I see that a year ago someone else had described the problem. I had assumed it would be fixed by now, but apparently not.