There is one guy and one woman (not together) who pass me on the MUP and always say "good morning". It makes me feel good and I respond with a good morning. I don't mind a bell or other sound, but the good morning is a nice touch. Then there is the crotchety guy who when I pass him and I give my bell a single ding, he rings his bell repeatedly as if annoyed. Now, I say hello to him.