Glassdoor allows to flag reviews that break their T&Cs, including sharing of company confidential information. Even disclosing that your CTO left, could be considered breaching confidential information. Many negative reviews are removed this way.
"Applied for a Java role, but had JavaScript questions. Tried to explain to interviewer there are unrelated things, was asked to come back when I learn more about Java. One star."
Might be wrong, but glassdoor does it too