Notice the base accuracy of my character (and the fact he's buck naked).

 

 

... now notice the spell accuracy...

 

 

Burst of Summer Flame adds +10 accuracy, which means that there's a +12 bonus to accuracy that's unaccounted for. It could be that spell casters gain an extra point of spell accuracy for each level (my character is level 12), but I don't recall ever seeing that mentioned or documented anywhere.

 

... yup, just confirmed my suspicions. Kana is level 11 and gets a bonus +11 to spell accuracy. Is this working as intended?

 Somewhere on the official wiki this feature is listed, so I'm guessing this is intended.