Maybe its the anonymous nature of comments, bad grammar school or never learning to diagram a sentence, but the number of people who can’t figure out when to use who or when to use that in a sentence appears to increase every day.
To review from the AP Stylebook
Who is for human beings and animals with a name. A person is always a who. Who is the subject and never the object of a sentence, clause or phrase. Example: The woman who rented the room left the window open.
That is for inanimate objects and animals without a name, including wild animals. That is never for people.
While my second favorite grammar source, Grammar Girl, does indicate a case could be made for using that for a person, she also writes, “I have to take the side of the people who prefer the strict rule. To me, using that when you are talking about a person makes them seem less than human. I always think of my friend who would only refer to his new stepmother as the woman that married my father. He was clearly trying to indicate his animosity and you wouldn’t want to do that accidentally.”
Got it?