I know admissions officers have released mixed statements about whether they look at a students social media or not. However, I’ve never heard about the student interviewers. After their interview with you, do they look at accounts such as Facebook and twitter to determine your legitimacy?
If you are talking about alumni interviewers, it depends on the interviewer. My friend interviews for her alma mater (Cornell) and she says her role is more of a promotional one for the university - to get students really jazzed up about it - and less an admissions tool, so I think it’s unlikely that she finds people on social media first. But if you interview for a school that uses alumni interviews for admissions more properly, then probably some interviewers would look you up and others would not.