I agree - the board has enough to do without getting involved in personal matters. Your concern with the super is that he does his job well. Don't give life to the gossip.
Unless moral turpitude is involved, stand down, back away and drop it. The behavior defined may go against one’s mores, but that’s not the value that tips the scales against the superintendent....
more I don't know about the board, but I'd say Mary's friend is a vile, gossipy busybody and no friend at all. Friends don't tell other friend's secrets.