a teaching assistant at a "top university on the East Coast of the USA" grades a paper

Huddleston and Pullum (scroll down)

When I say "no accountability," this is one of the things I'm talking about: a teaching assistant who does not know what the passive voice actually is given the power to grade student writing.

the passive voice files

Rodney Huddleston and Geoffrey Pullum on the passive voice:

In truth, the passive is very often exactly the right way to frame a clause in a particular context, and all competent authors use passives frequently. The people who recommend against it use it themselves, even while talking about how you should not use it. For example, in the act of explaining that you should "Use the active voice" because it is "more direct and vigorous than the passive", William Strunk and E. B. White assert that "Many a tame sentence . . . can be made lively and emphatic by substituting a transitive in the active voice" (see section 14 of their book The Elements of Style). Their sentence defies their warning; it contains an instance of the passive voice itself (can be made lively and emphatic).