> Is there any evidence they are directly using race as a factor in admissions and not factors that are strongly correlated with race, such as socioeconomic status and region of the country where the applicant lives?

I can't speak to how Harvard works specifically, but from what I've seen elsewhere if you're an underrepresented minority your application will get flagged and go through a different process where they take a deeper look into your background. For a white applicant who isn't a recruited athlete or flagged for any other reason, the admissions committee most likely makes a yes or no decision in 3 - 5 minutes just based on your GPA, SATs, and reading the first couple paragraphs of your essays. If your application gets flagged for some reason (being an underrepresented minority, a recruited athlete, letter from a big donor, etc.) then they'll actually take a deeper dive into your background before making a decision.

The colleges also get their simulated US News rank updated a couple times per day based on the GPA and SAT averages of students admitted so far, so what you need in terms of basic stats can vary substantially depending on whether your application gets read in the morning or afternoon.

  Is there any evidence they are directly using race as a
  factor in admissions and not factors that are strongly
  correlated with race

In my country, anti-discrimination laws include "constructive discrimination". So you can't deny a person a job for being black, and you also can't deny them a job for having curly black hair and thick lips.

The 'likability' factor is the strongest evidence of racial animus by Harvard. From the NYT: "Alumni interviewers give Asian-Americans personal ratings comparable to those of whites. But the admissions office gives them the worst scores of any racial group, often without even meeting them, according to Professor Arcidiacono."

https://www.nytimes.com/2018/06/15/us/harvard-asian-enrollme...