Certain spells can strike outside of their targeting reticule, Hail Strike is the biggest offender I've noticed.
There's a Ground Smash skill book that can't be learned if you have Battle Stomp. They seem like the same spell but Ground Smash does slightly more damage, I would guess it's an outdated version that was left in the game.
If you teleport a certain character in Fort Joy and teleport him back to you before he runs off, there's no indication that anything untoward happened and the character just ask you to use teleport again.
High Judge Orivand didn't die despite having 0 hp. Reloading before the fight started fixed it for the next fight.
You can't learn a skill while you have an item equipped that grants you the skill, bug or possible quality of life improvement.
No reaction from Fort Joy prisoners to killing all the Magisters aka liberating them.
