If you don't crash, you can't get upset!
If someone shouts Marshall when there car crashes, fair enough - even if it's still spinning through the stratosphere - sometimes you dont hear or see it. Shouting anything before or after "marshall!" (other than behind you) is out of order and said driver should be penalised!
Maybe some recognition for Marshall of the day at the end of a meeting will proactively encourage good marshalling and it thanks the thankless of all tasks!