I have always flashed trucks over whether I'm in the car or motorhome. Sometimes the truckers would give an 'appreciation' flash back, sometimes not.
On our previous coach, I had to turn on the headlights to use the flash feature for the headlight button to work on the steering wheel. The courtesy marker lights flash button would work without the headlights turned on.
The Dynasty used a fairly old fashioned type high-beam stalk indicator where you couldn't pull the stalk in to flash the brights, the lights had to be on.
On the new coach, it's like a car, with the headlights off (daytime running lamps on), you can pull in the stalk inward to activate the high-beams. About 80% of the time, the truckers will give an 'appreciation' blink of their tail lights or move their turning signal left and right a few times.
When the truckers flash me over, I will turn on my hazard lights a few times in appreciation.
MM.