I wonder how many times I have encountered these sorts of things and then changed them from being correct to incorrect in my documentation. Some of my favorites from the site are:
Using “who” for people, “that” for animals and inanimate objects
In fact there are many instances in which the most conservative usage is to refer to a person using “that”: “All the politicians that were at the party later denied even knowing the host” is actually somewhat more traditional than the more popular “politicians who.” An aversion to “that” referring to human beings as somehow diminishing their humanity may be praiseworthily sensitive, but it cannot claim the authority of tradition. In some sentences, “that” is clearly preferable to “who”: “She is the only person I know of that prefers whipped cream on her granola.” In the following example, to exchange “that” for “who” would be absurd: “Who was it that said, ‘A woman without a man is like a fish without a bicycle’?”*
“Since” need not always refer to time. Since the 14th century, when it was often spelled “syn,” it has also meant “seeing that” or “because.”
Nouns are often turned into verbs in English, and “reference” in the sense “to provide references or citations” has become so widespread that it’s generally acceptable, though some teachers and editors still object.