His reaction reminded me of my affinity to old-school behavior:
After my greeting and our eye contact, he stopped walking for two seconds and leaned forward, expressing his appreciation.
It was a sincere moment that obviously made an impression on me.
Takeaway: You don’t need to have a stick in your ass to be formally nice, you can just take a second or two and appreciate when people are treating you nicely, show your appreciation. It can be easy to forget although it’s not hard to do.