I think I'm going to go with the advice in the book on violations of the Laws. It's intent that's most important. For my campaign, a situation like in Grave Peril where Harry sets the ballroom on fire wouldn't force a character to take the Lawbreaker stunt. The fall to darkness should, in my opinion, be a matter of choice. Becoming an evil, twisted warlock should be about the conscious decisions to carry out certain acts, not stumbling into it accidentally.
Of course, that doesn't mean the
Wardens will see things the same way
As for losing Refresh, I always keep in mind that running to 0 Refresh doesn't mean you're "unplayable" or evil. It just means your character has become so driven by his nature that he longer has free will in the same sense. A character can be the purest good in the world, then lost his last Refresh point, and then dedicate his life to wiping out evil, or to quiet meditation.
A wizard with a lot of refinement who has a slip and starts a fire that kills someone accidentally shouldn't have to take Lawbreaker, and the rules do allow for groups to decide how to handle that themselves.
Now, a wizard with a lot of refinement, having dedicated so much of himself already to perfecting his craft, and then in a fit of rage summons fire to burn a murderer to death, well, he doesn't necessarily become a black-cloak-wearing evil warlock. The player might decide that the character gets a taste for killing and realises how potent a killer his years of study have made him. Alternatively, he might be repulsed by what he has done in violating all of the teachings he has learned, to the extent that he goes to live in seclusion where he can't be tempted anymore.
It all should depend on the character's Aspects and how the player wants their character's time as a PC to end.
