For example, in college I got a bad grade on a history exam.
The biggest part of why I got a bad grade was mixing up two similar sounding words in an essay question, which I vaguely remembered the professor might have made a big deal about not making that particular mistake in a class one time, but I couldn't remember the answer to the question if the question was using the word I thought it was, so I chose to write the answer as if the essay question had used the other word (I think it might have been about the British vs French versions of Parliament, something like that). This essay question was one of a set that you were free to choose from, as long as you answered a specified number of questions. Because I was pretty sure my answer to the first question was wrong, later in the exam I came back to this essay section and managed to answer enough other questions that I was one over the number that had actually been requested. I figured if it happened to be right it could only help my grade, so I left it there rather than crossing it out, and left a brief explanation as a footnote, requesting that that answer be discarded if only the specified smaller number of answers could be factored into the score.
As it turned out, that answer was marked wrong, and I got a pretty bad grade overall on the exam. The marked exam had no visible points accounting, so I didn't know how the grade was being calculated. I thought it seemed unfair that my footnote hadn't been considered, so I went to office hours to ask for a better grade on that basis. I got one, and I was surprised by how much, a full letter grade higher, just for that one question being discounted. This was actually upsetting to me though, I wanted to complain, because that essay section was just one part of a larger exam, and it seemed like that meant that making this one particular word mixup mistake the professor had a pet peeve about gets people marked down a full letter grade, and so you are penalized heavily from following the exam advice everyone gets drilled into them to always prefer putting an uncertain answer to not answering. Also the idea that he was probably just eyeballing the grades and there was no per question points accounting. It just seemed very unfair. But I kept my complaints to myself, since I had already gotten the best outcome I could hope for from that meeting and didn't want him to change his mind. I wonder if it was worth it though, since these events are now part of a rotation of things I sometimes spontaneously think about and feel a little indignation and imagine things I could have said instead, even though it was years ago and is irrelevant to my life now, and even though I think past me was likely taking grades too seriously.
Is that weird? I'd like to hear about it if other people also have little pointless grudges that they can't let go.
Yes, a lot, it's my favorite hobby. I like trying to make good arguments, appreciating when other people make good arguments, and pointing out bad arguments. Topic doesn't matter too much, though maybe free speech is the one I get most heated about, especially the idea that arguments are worthless and should be suppressed.