Generally I wave or say hi to other riders and even pedestrians when o0n MUPS. ON streets, when I am close enough to riders or pedestrians I also say hi or wave. Some respond, some do not. I like to be friendly but I gather that not everyone likes to be. I do meet some riders who look so serious or grim that they do not invite a greeting at all. Some pedestrians even look a bit hostile, as if they would be damned if they would greet me. I like being friendly and feel good when I meet others who are. But, each to his own.