For the first time (I am a relatively junior professor), a student has asked me to write a letter of recommendation for him for graduate school application in the US. I was glad to do so, as he is an excellent student who has performed research with me - we have authored a paper together.
On going through my letter now, it seems a bit ... unnatural. I have used the same adjective on multiple occasions - I only know so many ways to say that a student is 'good' at something. I am also sure that some of my word-choices will be noted as peculiar to the native speaker - most of my English writing experience is in academic contexts. While comparing to random examples that I have found on the internet, my letter seems boring and dull. I am also sure that my letter will have grammar errors of some form or another.
I wanted to know how admissions committees avoid having biases towards letters written by more talented writers, or by native speakers. If you were to put two letters having similar contents in front of me - one written by me and one written by a British or American or any other native English speaking professor, I would say that theirs is definitely superior, and I would feel more positively to their student.