I've got to admit I try and nod when passing another bike coming the other way. And try and wave when passing a fellow biker going the same way. But I don't when on the motorway (to busy avoiding useless car drivers, its mirror, signal then manuvour)
Oh I'm not bothered what type of bike it is, I've ridden and loved them all.
* could the people who don't say thank you when you hold the door open for them be the same bikers who don't wave?*