May Jews bow as a courtesy?
This custom can be further traced to Exodus 20:5 - "You shall not bow down to them or serve them." - while literally talking about idols, the prohibition was extended to monarchs who were seen as divine, or as extensions of divine power.
A number of years ago, though, I travelled to Japan, and faced a different cultural reality -- bowing not as an acknowledgement of superiority, but merely as a polite courtesy among equals. After a brief period of discomfort, I decided that the Japanese polite bow was simply not the same as the prohibited bow-to-authority, and started returning the bow of anyone who bowed to me. (I'm aware that there is huge cultural nuance in how shallow or deep a bow is, but I wasn't far enough immersed in the culture to do more than a bare minimum of politeness.)
Now we come to 2020, the first plague year in most people's lifetimes, where norms and customs are changing rapidly. In my area masks are mandatory, and will likely remain mandatory for quite some time; losing the ability to smile at people makes other gestures of courtesy and politeness feel even more important. I have adopted a modified bow with my hands over my heart as both a polite greeting/"thank you" and as a subtle way to keep people from trying to shake my hand. (In the course of my work I interact with many people, and it is important to me to avoid contact as much as possible.)
Is this Halachically acceptable?
And the bigger question: is the prohibition on bowing an actual part of Jewish law, or merely a tradition?
(Please note that while I bring up Mordechai and Haman, this question is absolutely not "Purim Torah".)