Comment:I prefer the use of "who" when the writer is referring to a person. However, my Gregg Reference Manual allows the use of "that" in certain sentences:
"Who" and "that" are used when referring to persons. Select "who" when the individual person or the individuality of a group is meant and "that" when a class or type is meant. Examples: She is the only one of my managers who can speak Japanese fluently. He is the kind of student that should take advanced math.
In the case of the "offending" sentence mentioned in DWT above, I suppose "that" would be the word of choice--but it would probably have "caught my ear" as I read it, and I would have made a (personal) mental correction.
By the way, Gregg also says to use "which" and "that" when referring to places, objects, and animals (distinction based on essential or nonessential clauses), but notes that "'Who' is now often used when an animal is identified by gender or a pet is identified by name."
On the other hand, I work as a proofreader in the print business, and the customer always has the final word. I have learned to be very diplomatic about how I word "corrections" questions, and persistent only if I believe the wording does not convey what the customer intends. So, "flags," yes; "crazy," no.
Author: Cassie Tuttle
The use of "that" instead of the personal pronoun "who" is one of my all-time biggest pet peeves.
Though such usage may not "break the rules," it's one of those phrases that hurts my ears. I've taught the "person who" versus the "person that" to ESL students and to in-house legal staff who attended my Grammar & Usage courses.
Sometimes, it's just a matter of principle.
It's funny that I always use the word "that" with "girl". Somehow "the girl that" tends to sound smoother than "the girl who"