I am not totally visualizing this situation. Can somebody explain it a little better?

If Boat S rounded the offset mark and bore off, still on starboard and raised their spinnaker on their port side, why did they not see Boat P?

Did Boat P hit Boat S directly broadside on Boat S starboard side, or what? Was there damage to the boats, as well as to the crew?

Also, the description of the incident makes it sound as though it is not a good idea to come in to the weather mark on port, even when you do know which is the proper weather mark -- "Every week we see boats come in on port tack at the windward mark. This incident was made worse by boat P making a mistake in identifying the wrong mark as the windward mark. This was an accident, though every week end we see similar incidents. Boats coming in on port tack to the windward mark without any rights."

So, does this mean that, when going upwind, to avoid getting into a collision with preceding boats that are now heading downwind, you should always go to the right side of the course and approach the weather mark on starboard tack from a considerable distance out?