Help required understanding this line from Haruhi Suzumiya novel

This is one of those sentences where in theory I understand all the grammar and the words, but im having trouble working out exactly what it means:

サンタクロース いつまで信じていた なんてこと

I’ve highlighted the particles here, as it’s a long sentence and it makes it easier to see

My understanding so far as as follows:
As for such a thing “Until when did you believe in santa clause?” (サンタクロース いつまで信じていた なんてこと)
as much as it does not become childish gossip at least (たわいもない世間話にもならないくらい)

now this is the part that i’m really struggling with

- is nominalising the clause before it “the ‘not turning into childish gossip’” and using it to modify whatever comes after it

どうでもいい - means “What ever way is good” or simply ‘it doesn’t matter how’

ような話 - is saying that the it’s a "X form "-topic, X being the bit that comes before

so the whole sentence is saying somehow “as for the question of until when did you believe in santa clause, it’s is an XYZ topic”

Can anyone help me understand how this all fits together?


We read this book a while ago in the intermediate book club, so it’s thread could be very useful to you if you plan on reading the whole thing.

Even more conveniently, someone asked about that very same sentence, and got some answers:

Hopefully those can solve your doubts.


Thank you so so much!!