Yup! Depends upon speed & circumstances but most times if it's safe to do so. Not often on major/ split highways though. I wouldn't really call it a "wave" in the accepted sense of the word. Here it's an acknowledgment, & consists mostly of merely taking ones hand from the left bar & more or less extending it out at seat (hip) level, Almost like you're pointing at the road a few feet from your bike. It's most definitely not a manic wave :banana:that could throw the bike off balance or be misunderstood as a stop or turn signal; that would be silly.
I can understand that in countries that drive on the left that it's more difficult to take a hand off the throttle, so maybe a nod becomes more acceptable & safer.
As for folks waving back some do some don't (mostly Harley riders). Their choice!
But Yup I do it & will continue to acknowledge fellow riders.