There's an etiquette to waving, you don't wave at frumpy vans, builders vans, Range Rovers even though their DRLs look like a T6's, you don't wave to campers running 16" Clayton's especially if they're showing 4" plus of air above said wheels...
It's a minefield as even the actual wave has to be at least mildly "Gangsta" and conveys so much more when as little effort as possible is put into the actual wave, see a typical drive by display from a Lowdown Transporters club member and you'll possibly catch a raised finger on the steering wheel and a slight look of disdain.
Obviously that is one extreme of fellow Transporter driver acknowledgement and camaraderie as is losing your shit every time you see another T van.
It's a fairly long apprenticeship but after a period of rejection don't simply withhold all future waves but use those remaining waves judiciously and never flash your headlights as this will cause the other guys signature designer DRL's to go out if he replies in kind and that bursts the cool bubble.
I actually wave at other T6's as I crawl past them on the motorway and that rarely gets a wave back so you might want to use your own set of rules, I do always return a wave though!
Edit and just for clarity, yes I do wave like a nutter!