George Duke wrote on Wed, Aug 1, 2007 10:23 PM UTC:
Blue Queen becomes playable with the proviso that Blue Queen can only
capture a Pawn threatening her. Blue Queen cannot actually be captured
even by a Pawn threatening her. Of course, there is no capture of Blue Queen at all simply because the one Blue Queen belongs to the player currently moving. So, the 'Pawn threat' is hypothetical, based on Pawn's
one-step diagonal-forward capture, with respect to the present position of Blue Queen. It prevents easy Pawn captures. Otherwise BQ moves like normal mad Queen including piece captures, checks and checkmate. Second mini-Rule is there can be no two-fold repetition. Two-fold repetition is not Draw, just dis-allowed and another move must be made instead. This prevents shuffling Blue Queen back and forth, but must also apply to moves not involving BQ, so caution for end-games. Those two requirements should move Blue Queen from thought experiment in games journal(originating 1950's) to playable game.