Traditions-wise, the general consensus appears to be that: In an open meeting, a non-alcoholic may introduce themselves, if asked to do so -- otherwise they should refrain from all sharing. The purpose of having an Open Meeting, which allows anyone from the general public to attend -- is so that non-alcoholics may attend "to listen" and see if they identify as an alcoholic.
Most meetings have what they call a "Blue Card" and is read before the meeting, along with the Preamble. On one side there is a Statement to be read at Open Meetings. And, on the other side, is a modified Statement, appropriate for Closed Meetings. It's typically the Meeting Secretary or Chairperson's or Leader's responsibility to make the announcement.
One of the additional things that was passed on to me, when Chairing or Leading an Open Meetings, is to announce "My name is Dallas, and I am an alcoholic. Can I see a show of hands of anyone else that identifies as an alcoholic?" Then, I note who didn't raise their hand -- and I refrain from calling on them. And, if they start to share, I explain the tradition and re-quote the Blue Card for them, as I ask them to refrain from sharing during the meeting, and to see myself or one of us AFTER the meeting, when we will be glad to talk with them.
This is something that will occasionally happen at OPEN meetings, especially when care has not been shown before the meeting starts -- to make the appropriate announcements. If it happens often -- the members in the meeting should have a Group Conscience meeting to decide if it would be more appropriate for them to be a CLOSED meeting instead of an OPEN meeting.
Also -- I've never been able to figure out WHY any AA meeting would be an Open Meeting -- if it is not an Open Speaker Meeting. Because any Open Meeting that allows Alcoholics Anonymous to share their stories with non-alcoholics is breaking the tradition of Anonymity for the alcoholics who are present.
I don't blame the non-alcoholic for sharing, in a situation like this, if: A. They have not been instructed to NOT share, prior to the meeting. And, B. If they have been called on to share. It is the AA Meeting Chairperson's responsibility to see that appropriate measures have been taken to prevent it from occuring.