Reply to it, but without being an arse. Something like:
Dear Dominic,
Thankyou for taking the time to reply.
I perfectly understand that it is common track etiquette to signal to the car behind that it is okay for them to pass. I’m not disputing that it’s a good idea to signal to them... it's just that the instructor could simply have asked me to do so and I would have obliged - I’m perfectly capable of using the mirrors and indicators. As a driver I find it a bit distracting when the front seat passenger reaches over to fiddle with stuff and a bit of an invasion of my personal space while trying to enjoy driving.
With regards to the day being an experience rather than a race, I entirely agree. I was not expecting to drive 100% flat out for every lap! However what I was expecting was to drive a few laps, starting off gently and slowly building up confidence to do a ‘hot’ lap. In reality I never was allowed to do more than 4,000RPM and 70MPH. That’s more like a Mondeo on the M4.
Clarkson said that the Ferrari 360 “makes a blood-curdling noise as the revs climb round toward the stratospheric red zone.”... however I only got to experience the first half of the 360's 8,500RPM limit and even that was done under duress and without any form of event or enjoyment.