“... impatient and discourteous drivers might flash their lights or even honk their horns, which is inappropriate ...”
Inappropriate? Discourteous? WTAF ...
Flashing headlights to request a slower vehicle to move over is a courtesy that has been around since cars started to have headlights. Of course honking one’s horn at highway speeds is fruitless as the car in front of you probably has their windows up and radio blasting making your honking unheard.
Having a dash cam is a good idea if a left lane bandit (LLB) is encountered. Your recording of a driver’s refusal to move over may be the evidence that gets a ticket for the LLB or jail time should road rage ensue.
Germans have been flashing their headlights at cars traveling too slowly in the left lane for decades. It means move over to the right lane. No one seems to get road rage from it. At least, they didnt when I drove there. And as I recall there were no speed limits in the left lane. That must have changed.