And those teachers deserve to have lower student ratings, because the quality of the experience for the students is drastically lower even if they learn the material at relatively the same level of competence. I myself have social deficiencies, and I don't expect people to give me sympathy points if I ended up lecturing a large class.
I fail to see how anything you've written about Coward's "cult of personality" is bad at all.
How can your teaching quality be proficient if you can't speak English well? Sure there are teachers who get unfair evaluations because they have a bit of an accent, but if you actually can't speak English well, how are you effectively teaching in English?
[0]: http://www.academia.edu/6126025/Expectations_on_Speech_Evalu...
Key quote from page 444: In a typical study in this paradigm, participants listened to 4 minutes of a tape-recorded lecture produced by a native speaker of standard American English. Some participants were lad[sic] to believe that they were listening to a North American NS[native speaker] instructor, whereas others were lead to believe that the instructor was an international NNS[non-native speaker].
[...]
[I]ndeed, listeners who were exposed to the Chinese/NNS guise perceived more of a foreign accent and scored lower on a recall test than those who were exposed to the Caucasian/NS guise even though the audiotape they heard was exactly identical (standard American English).
I've had instructors who had accents but could still speak English very well, and many people just dismissed them outright as unintelligible without even trying.
But I've also had instructors who just weren't fluent in English (mostly grad student instructors). When VanillaSwirls said they didn't speak English well, that's what I was thinking of.
Teaching is intrinsically tied to communication. Failure to communicate, failure to speak english well, is a failure in performing the art of teaching.
Any benefit the teachers see from knowing their ratings is purely so that they can improve the experience for their students. If a professor can't speak english well or have social deficiencies preventing from communicating clearly, they aren't excellent teachers.
There are professors whose teaching quality is actually proficient and sometimes excellent, but whose student evaluations are marred by the fact that they can't speak English well, they have social deficiencies (e.g. Asperger's syndrome), etc. Student evaluations are flawed in the same way intelligence tests are flawed; student evaluations favor professors who speak and communicate most closely to the popular consciousness of students at the time in the same way intelligence tests are biased against non-native test-takers (some questions posed on intelligence tests may use culturally native objects).