Long story incoming:
I was always a good, respectful student in college. I generally got good grades, but even when I didn't I still was on great terms with the professor. I've even had professors offer to write me a glowing letter of recommendation despite not having received the greatest grade in their class. I think this is because I always tried very earnestly, put in a good effort, and was always respectful.
So it was a shock to me when I was taking a Brazilian ethnography course the second semester of my junior year, and near the end of the semester I found myself in the professor's office as she mercilessly chewed me out, grabbed all my papers from the semester, and slammed them down on her desk in sheer anger. I'd went from having never had a conflict with a teacher before for my entire life to being borderline attacked for simply asking a question about a grade that I didn't think was fair. I was completely powerless. I had to sit there in silence and just take it.
It was a long journey up to that moment, but I'll try to simplify. The class was built around a semester-long research paper which included an annotated bibliography. We were to build our set of sources to use over the course of the semester. Part of this involved weekly writing assignments on topics relevant to our research where we were encouraged to try to find sources to use for our final bibliography. These were turned in and personally read and graded by the professor.
Whenever I found a particularly good source that I knew I'd want to use for the paper, I would write the annotation along with the weekly assignment. It just seemed sensible for me to distribute that work over the semester. I thought others were doing it as well. I let her know, and every week she read my annotations and provided feedback. My final bibliography was thus mostly a compilation of annotations I'd already written over the course of the semester with modifications based on her feedback. Mostly all of her feedback, though, was very positive and encouraging.
I was really confused, though, because I noticed that some annotations that I'd received very, very positive feedback on earlier had been graded very, very negatively on the final bibliography. These were extreme inconsistencies in grading and feedback, flat-out contradictions in fact. So I asked if I could meet with her to ask about that. And that's when she went off at me.
She really ripped into me out of nowhere. To this day I don't understand what she was upset about. It seemed she was mad that I'd been writing the annotations over the semester and then compiled them together for my final bibliography, even though she had encouraged me to do it and had repeatedly given me positive feedback. I actually thought everyone had been doing this. She had never once, even a single time, indicated that I was doing something that wasn't what she expected, for the ENTIRE semester. I asked her why the same annotation was viewed so differently then and now, and she claimed that, since the annotations weren't officially part of the weekly assignments, her official written feedback in red ink was meaningless and invalidated. I had "misinterpreted" her repeated praise and positive feedback over the entire class. She had actually hated the annotations I'd been writing, but had communicated that to me by writing that they were "great!" and apparently holding back constructive criticism.
She was absolutely unwilling to budge. She refused to admit she had sent extremely mixed signals to me on my annotations. I was very respectful the whole time as well, basically holding back tears since I'd never experienced such antagonism from a teacher. I tried to talk to the department and they wouldn't take me seriously. They just saw me as a little brat who obviously was entirely to blame for everything and therefore didn't deserve even the slightest bit of consideration.
I went on to get an A+ on the final presentation, an A on the final paper, an F on the bibliography, and a D in the class. There was nothing I could do about it, and my transcript and GPA both took a massive hit.