Omitting 'ka' particle from a question.

great post johnny, you've cleared it up somewhat for me (although still a little out of my league).

It still retains the grammatical function of marking off clauses (i.e. 姉ちゃんはどうしてあんなやつと付き合ってるかはオレ に分からないよ),

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It used to bug the stylist in me quite a bit to see か and のか used so inconsistently within sentences -- at times even the same one -- but I don't think it has the same implication of being either polite or blunt as a sentence ending particle....so I'm really trying not to let it get to me quite as much...