It is Standing Order 19.
Standing Order 19, which is met with a side note in the Standing Orders, states that on points of order, the Speaker may allow a debate. The entire standing order reads, and it's very short:
Any Member addressing the House, if called to order either by the Speaker or on a point raised by another Member, shall sit down while the point is being stated, after which he or she may explain. The Speaker may permit debate on the point of order before giving a decision, but such debate must be strictly relevant to the point of order taken.
That's exactly why I was pursuing a relevant, germane argument earlier related to the Standing Orders and to Marleau-Montpetit. You are empowered and--as it is strongly implied by the spirit of this standing order--required to allow a debate on points of order.