The way in which Heng describes race is fairly similar to how I would describe it: as a means to establish a hierarchy for differential treatment. It is important to include how race functions practically in society because that part of it can get lost when discussing its cultural aspects. My only concern is that the explanation only covers part of how we experience race in modern-day America, specifically for those who suffer from the negative effects of racial division. While Heng perfectly explains how race is utilized to form a hierarchy among groups of people, her definition of race excludes how it is used as a form of empowerment for those at the lower end of the hierarchy. For many marginalized people, race is the only way to cope with inequality. The communities formed by racial divisions offer a kind of support that spans across all other barriers such as religion, gender, class, etc. The thought that someone hundreds of miles away can relate to the experiences that you have had can be therapeutic. By having a group of people who understand what it is like to exist as a marginalized person, you are given a sense of validation. Because of this, I think that both the logistical and emotional effects of race should be considered equally when attempting to define race.
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.