I wave at oncoming riders when I can be bothered (and I generally try to answer a wave with a wave). Having said that, if I'm riding home from a 220km ride into a monster headwind, I mightn't feel like waving, so unless one is forthcoming from the other side, I mightn't bother.
Re: passing. I have been both the passer and the passee on many occasions. When I'm the passer I generally wait until I get the opportunity and run wide of them on the right (the left for those in the US). I don't bother shouting at them because I'd prefer not to see people do that to me. I might say a quick "G'day" or ride with them for a while if our speed is compatible, but otherwise I'll just be on my way quietly.
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I am clinically insane. I am proud of it.
That is all.