would pO (with other appropriate modifiers, of course) allow castling with an intervening piece?
Sort of. I chose that as the notation of 'Fast Castling', which allows the King to jump over arbitrarily many pieces or attacked squares. The Rook would then move to the King's square of origin, though. So it is not normal castling that can hop.
The O atom is treated somewhat differently from other atoms. (E.g. the range indicator specifies the exact number of King steps, not the maximum as ranges normally do.) It had to, for making the combinations useful.
Sort of. I chose that as the notation of 'Fast Castling', which allows the King to jump over arbitrarily many pieces or attacked squares. The Rook would then move to the King's square of origin, though. So it is not normal castling that can hop.
The O atom is treated somewhat differently from other atoms. (E.g. the range indicator specifies the exact number of King steps, not the maximum as ranges normally do.) It had to, for making the combinations useful.