After some useful feedback from our users we added a new feature today.
We have added a new group setting which allows you to choose whether the sender of a message will receive that message. With this setting switched off (the default) the behaviour most closely matches what traditional group email lists do i.e. you send a message to a group and everyone in that group receives the message except yourself.
However if you would like the sender of a message to also receive that message, maybe for audit purposes, then enable this option and everyone will receive the message including the sender.