I think it is important to practice polite earbud use when in public. This entails the following rules:
In-particular, I think transparency mode on most earbuds is socially too uncomfortable and unknown as to whether or not it's on.
Removing earbuds is not just about improving your ability to hear others – it's about signalling that you actually want to hear what others have to say and you are actively listening.
As a good example, even if I'm leaving a store, I temporarily remove my earbuds just to say thankyou to staff as I'm leaving, and put them back on when I'm outside.