Almost any of them?

Asking a candidate about how fat someone is definitely does sound like something that would get an interviewer in trouble.

Many people are deeply insecure about their weight, many women feel very uncomfortable when men make any comment about anyone's weight, body or appearance. The candidate might post on Glassdoor or LinkedIn about the hostile (and possibly sexist or "bro-y" or noninclusive or discriminatory) environment.

Even aside from the HR type concerns, it could legitimately negatively impact the candidate's performance. Imagine an overweight applicant being asked that question, feeling flustered and embarrassed while answering "... about as fat as me?" and then trying to reverse a linked list or whatever as their next question.

smells like 'can't say anything anymore' coded whining.

No I really would be uncomfortable at work asking that question to an interviewee.