You can use skills sometimes after mirrors hits you
Sometimes mirrors hits you even if you sub outside of the mirror zone.
fixed mobs getting hit who are outside the mirror zone.
I think you should be able to use skills inside mirrors just not shunshin.
JeanSqribe yes literally in naruto, both sasuke and naruto used skills in ice mirrors, but is the damage automatic like if a gaara used sand shield in mirrors would be still take the damage from getting caught in them?
If you use Kaiten/SandShield/Crow? at the right time you would be protected from the damage, I haven't tested this but logically that's what should happen 🙂