[jdrek1]

Skin color and (facial) bone structure for example. Like it or not, but humans have adapted to living in different climates and have different ancestral lines. Take a picture of an average black person and edit to white skin, it will still not look like a white person.

As the commenter above you already said, this is not a bad thing. People on _hacker_news should be able to understand that being able to define the ==/!= operators on something does not automatically mean that you can define < and >.

[dofm]

All white people are different from all black people in the same way?

They can be told apart like this, absent skin colour?

[jdrek1]

It is more obvious with some and a bit more nuanced with others, but in general yes. Just like you can typically see the flat/wide nose in Africans and Asians but not Europeans. Again, there is no implication of one being "better" than the other here, but don't pretend it's impossible to categorize people like this.