This is exactly why I was afraid about them implementing an Alignment system. Larian determines whether you break your oath or not, but oaths can be a bit more subjective and not super black and white.
Here's how it reads, and my interpretation in brackets:
Tenets of Devotion
Though the exact words and strictures of the Oath of Devotion vary, paladins of this oath share these tenets.
Honesty. Don't lie or cheat. Let your word be your promise. [Straight forward for this one. Not much room for interpretation. Don't intentionally deceive. If you lie unintentionally, you haven't broken your oath as long as you admit to being wrong as soon as you are able. So, example of oath breaking would be telling Minthara you'll help her slaughter the grove and then fight her instead when she gets there.]
Courage. Never fear to act, though caution is wise. [Don't know how they'd implement this in a game since the devs can't know what a player is thinking, but essentially the player would only break an oath here if they allowed fear to keep them from doing something they should do. This is REAL subjective, though, and could probably only be done in dialogue with warnings. Example would be option says "Nevermind Ethel. We're leaving. [Because you are hesitating, doubting whether you can actually win this fight - this will cause you to break your oath."]
Compassion. Aid others, protect the weak, and punish those who threaten them. Show mercy to your foes, but temper it with wisdom. [Temper with wisdom. That's the key here. Saving the grove keeps your oath. Siding with Minthara breaks it. Saving a person about to be executed by Ragzlin and his cultists in the heart of their lair and you don't even know much about him - he could be a terrible person for all you know - would not break your oath.]
Honor. Treat others with fairness, and let your honorable deeds be an example to them. Do as much good as possible while causing the least amount of harm. [Again, somewhat straight forward. Don't be disrespecting others and mouthing off and attempting to trick them. If it's shifty, it's not honorable.]
Duty. Be responsible for your actions and their consequences, protect those entrusted to your care, and obey those who have just authority over you. [If your party member dies, and you did something that left them exposed and that's why they died, you broke your oath. If they died in combat by chance, doing as your party planned but things just went wrong, you didn't break your oath. Example. I send my paladin up ahead to attack a rothe and recklessly trigger more duergar to attack my party, and as a result Lae'zel dies, that's my fault because I recklessly attacked the rothe. Oath broken. If my party is fighting Gith and Lae'zel runs off to fight 3 of them by herself, my paladin has not broken his oath.]
