and is all the cleavage at the Renn Faire as historically inaccurate as most everything else there?
There was quite a bit of décolletage in many medieval and Renaissance styles, and outright bared breasts in some periods and places, but when present such fashions tended to involve square necklines.
For some reason everyone assumes that for the entire history of Western Civilization from roughly the Fall of the Roman Empire up until the 1920s or so, it was just as prude as it had been during Victorian Times, which of course was not the case.