Half way through my third-year I just got my surgery rotation grades back. Along with it came a "Dean's Letter Summary". I suppose these are the collective comments of the residents and attendings I worked with that will later be used for residency application purposes. If a student doesn't do well on a rotation or even just less than average does it reflect in these letters? What are the code words that residency program directors look for to know that applicant A is better/worse than applicant B? I have a hard time imagining that anything bad or sub-par could be written about students in these letters.
It's variable how your Dean's letter is handled by your school, but for the majority (IMHO) it's rare for a poor comment to be written in the section fo your evaluation that the attending knows will be used in your Dean's letter unless
A) It's a mistake (heard of cases where they wanted to say something "off the record" like "Work on making notes more concise" and it was written in the wrong section
B) They REALLY REALLY mean it.
I know for B, if you write something negative like "difficult to work with" "did not perform up to his potential" in the Dean's letter section, most of our course directors actually go and talk to the attending to confirm they want that in the Dean's letter and that it is a fair assessment of the student. That's not to say negative things don't make it in if you deserve it, but it's an additional filter.
That said, even though a lot of negative comments don't make it in to the Dean's letter, it is usually a case of "Who is more better than the other?" People will tend to have good comments, but some will have superlative. I don't think there are hard and fast "code words" that span across all schools (Which is objectively better: Fantastic, Outstanding, Excellent? Who knows.) But there are "shorthand" type things. Off the top of my head some big ones are saying things like "Would love to keep on as an intern/resident" "Performed beyond his/her abilities as a third/fourth year" "Was a valued member of our team" "Would make an excellent [insert field attending is]". Those are some especially strong comments I think residency directors like to see.