I think replying to any message generated out of the group is going produce a message that is visible to the group, as a whole.
As I said earlier, I think any dealer has to have some private email account to which definitions are sent.
The second level is the sender. The whole things also depends on what email goes in the To: line of submission email.
If you have a players Google Group address in your address book, that may very pop up as son as you start entering his/her name.
If you accept that without checking it against what the dealer posted in the announcement, then the mid-address is your fault.
The safest thing to do is to type in the whole address, as specified in the announcement.
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With the right music, you either forget everything...OR, you remember everything.