This is truly a silly pet peeve, but a lot of grammar mistakes. Like writing "should of" instead of "should have," that sort of thing always stands out to me. Probably because linguistics/grammar is one of my weird fixations/special interests, so I can't help but think about it. I never say anything to the person though cause I don't wanna be that guy
Mismatched socks also bother me??? Actually mismatched and misplaced things in general irk me a little because of my neurodivergent ass. I've tried wearing two different pairs of socks and noped right the fuck out of it once they were on lmao