I fully agree with your suggestion mrknowall ref a warning sign to members advising them that they are in danger of contravening the "unwritten" rapid posting regulation, although I have no idea how practicable it's introduction would be.
I was similarly banned for a short period recently, when my only transgression (presumably) was to answer several questions on different threads in the Q&P section, within a short time period.
This penalty has also been applied to other members of this section for similar incidents.
It does seem unreasonable to be exiled for simply providing the answers to queries raised ... and your suggested warning sign must surely be worthy of consideration by the "powers that be"!