Not in general, maybe, but if someone posts their first name in one place, post about their neighborhood in another place, and mention their job in a third place that's enough to uniquely identify them. Or who's to say there isn't a comment with someone's full name and address?
Unless they manually scan all comments for PII, there might be PII in any comment. Even something innocuous like a picture of a sign can doxx someone, so it's not obvious, either.