Regarding the Ferrari on the Autostrada; I lived in Italy for 2.5yrs, its not just Ferraris. Any car approaching quickly from behind will flash you (even if you are already going 100mph)- the polite ones only once or twice, the impolite ones repeatedly. The worst are the X5s and Cayennes with their HID beams mounted much higher than other cars. Even German cars in Italy will do this, while in Germany they’ll leave the left blinker on as an indication that they are on a “high speed run” and resort to flashing only if necessary.

I learned of another practice while working in Oman where truckers would - having noticed a car queuing behind them on the highway - put their right blinker on indicating it was safe to pass (as they could see ahead, and you the follower could not), while a left blinker would warn that it was not safe to pass. This system requires a lot of faith in your fellow man. Since most of the truck drivers were from the subcontinent I assumed they brought this system with them.

* One cultural issue is what do indicator lights mean? In some countries/cities, signalling intent is weakness. It’s a request “please can you let me change lane” that is up to those in other lanes to ignore. But it some countries -and France springs to mind- it’s a signal of intent. If you indicate on a french autoroute, it means you are warning people your vehicle is about to change lanes and they should create space. There’s no request involved.

Waving (or nodding in places that drive on the left) is common to bikers the world over. It is an affinity thing, same as when you sit next to another rider at lights you exchange greetings. Agile mammals in a world full of dangerous lumbering dinosaurs, we acknowledge each other’s choice to ride, even when you have to share the road with cars.

I find cyclists do it too and for the same reason as motorcyclists.

Due to more arm visibility motorcyclists may have more signals. On the local racer roads there’s “Slow down for hazard” which is patting the air with your hand, used for cops as well as for bad road surface. The specific cops ahead signal is arm up in the air with first finger extended and rotating hand to suggest a rotating police car light. (That’s an old one of course, but still in use, the same way level crossings are marked with a steam train graphic here)

“Your indicator is on” is arm extended so fist can be seen, then open and close your hand at the rate an indicator flashes.

I do wish there was a “turn your fog lights off you wanker” signal, but even if there was they wouldn’t take notice.