This is an exceptional point. I really like how you frame the strength of Heng's intervention here (that she focuses on the function of race, which keeps it from getting too abstracted from lived experience), and this connects sharply with your insights into function of community in racial divisions. What this makes me think is that what's very much needed in the wake of work like Heng's is research into lived experience of communities living under racial oppression. There's some very good work on this in the Middle Ages in terms of Jewish communities and few other groups, but, to my knowledge, there isn't a text that does the exact work you're calling for here.