It’s funny how I recognize all this. I’ve started to bike more and more, about 100 km every saturday and sunday, to get fit for my tour. So I meet a lot of cyclists of different types. And it’s true that there is a certain category that won’t reply on my nods. Otherwise I must say it’s great with this friendship on the road.
The only ones I don’t say hello to (based on trial and error) is the farmer on his way to the barn or the couple on their way to the grocery store and the like. I just don’t feel I have that much in common with them, just because they have a bike. But I would always reply if someone of them said hello (which have never happened).