It has to be very insignificant to the point you think that people wouldn't care about that issue other than you (unless that issue of course would make people agree with you.) It can be from a certain plot that really has no bearing on the chapter, supports that you feel shouldn't be popular but suddenly is or the gameplay mechanics.
I'll start. I don't like tea time when specifically post-time skip. My problem with that is their voices. I just did tea time with Ignatz and I frowned when I had to hear his girlish voice (I'm playing in Japanese Dub). I can't stand through that tea time at all from the beginning until the end because their voice didn't match up with how they look. I want Ignatz voice to be all Chad like but I didn't get that.
And you know what it's even funny? When you give them a present, their voice would go back to their post-time skip voice. And then when you exit the tea time, their voice is STILL their pre-time skip self. I don't know if this issue also persisted in the English Dub but I imagine it's also there.
So yeah, that's the one small thing that REALLY bothers me. I can't stand to hear their pre-time skip voices in a tea time but in post-time skip. Especially if it's in Japanese Dub where all their voices becomes deep (minus church members excluding Cyril and Flayn).
There's also another one which is getting an increase or decrease support points with Jeralt even though there's no support for him. I could make an explanation but I think you get my point.