I can only remember one instance in which I noticed a black person in a CS class*. He clearly wasn't connecting with anyone else there on a cultural level, but he was making much better observations and comments than most anyone else (some of the people who sounded like a Racial Realist's dream programmers were answering simple questions with facepalm-worthy wonkiness).

What stuck out to me most, though, was whenever the teacher would elaborate on or correct any of that black student's responses, the student would respond to everything with a very submissive and depressed-sounding "Yes sir." He didn't sound quite so broken in any other context as that. He disappeared halfway through the semester and I have no idea why (was he better at in-class discussion than tests or homework? Did he drop the class because he didn't like it? Were there other classes he wanted/needed into which conflicted with it? Did he quit school entirely?)

It seemed abundantly clear to me that, of all the students that spoke up during class, this one was probably in the top 3 in terms of understanding the material, at least in a classroom context. There might have been problems, but I wouldn't dare pin them on intelligence. Culture seemed dramatically and obviously a source of tension. If there were others, they were not where I could observe them.

* There could have been others I missed, or that were in previous classes who I just forgot about. I can only identify race based on accent (which I should point out is not genetic) or if someone else points it out without being contradicted by other evidence. ... Well, and names, sometimes, but those aren't genetic, either.

You know, sometimes the troll doesn't even need to make people believe their point to win; they just need to make people treat their point as if it was seriously worth debating.