i sure have! that moment with the butterfly marks is great because it's subtle if you don't know what it's saying and extraordinarily obvious once you do. i was so fixated on the themes of obligation and inescapable fate from the moment that magic circle was introduced, and it really did help me unravel the identity and motive of the culprit (though it tripped me up for a bit and i really wanted it to be natsuhi!) and sometimes a chain is just a chain, but even then, this is umineko so it works on multiple levels.