So to summarize:
Lesson #1. If you are going to give orders to units at night, and it's important they act upon them pronto, then you had better set their rest option to None.
Lesson #2 - Check fatigue Levels and Straggler options before ordering attacks
LESSON NUMBER THREE FOR BFTB NOOBS LIKE ME: To reduce the likelihood of "HQs Leading the Charge" incidents uncheck the stragglers box, forcing the HQ to wait for exhausted units before launching an attack or moving towards contact with the enemy.
Wow. Well. Like I said, I am always worried about throwing in a red herring.

I hate it. Damn. Damn. Damn.
Anyway, great, great game.
There are a lot of intricacies to learn here. "Set rest to normal in this situation"/"Don't over exhaust your troops"/"Don't set to no rest in others". But it is only in its complexity that you can offer players options. So I fully support this. But, as you said, it probably is worth mentioning in tutorial videos.
Actually, I had been ordering movement at night with "no rest" options as I realized that was the only way to get troops to really move in the middle of the night. But I had been "disciplined" (in a nice way!) by fellow posters for issuing no rest orders as a possible reason for non-compliance by my units.