I don’t live in Brooklyn and I have spent very little if any time there, so I do no know how people greet each other on shabbos or any other day. Where I live, which is a very frum community as well, men will nod to me and
/say good shabbos almost every time. I don’t think anyone has ever walked passed me on shabbos and put their heads down. I am talking about very yeshivish men, not chassidish maybe it makes a difference. This is a reason I love me neighborhood. I don’t know many people besides my friends but everyone is friendly. And 2 millisecond ” good shabbos” or a pleasant nod doesn’t do any harm. This has never led to IMO any bad behavior on my Part and I would assume on the part of then men who wish me and my husband a good shabbos.