When the か particle serves as a parallel/disjunctive marker (A or B = AかBか), is there a strict requirement that it must follow each noun? Or when joining more than two items, should they be replaced by a comma?
That is, for "A, B, or C" would one use "AかBかCか", or – as I've seen happen with や – is it considered better to simply use a comma "A, B, Cか..." (or would it be "Aか, B, C..."?).
As a related issue, the answer here mentions that when か is then followed by certain particles such as "は, が, に, を" it seems to be OK (or even necessary) to drop one of the particles. Quoting the example here:
誕生日はお母さんかお父さんかがケーキを作ってくれる。 (x)
誕生日はお母さんかお父さんがケーキを作ってくれる。 (o)
誕生日はお母さんかお父さんかケーキを作ってくれる。 (o)
Is this purely an artifact of casual speech like other particle dropping, or is it actually necessary to sound correct even in formal speech? And for which particles is this necessary? In particular, when using parallel な-adjectives instead of nouns, which of these would be preferred:
有名か豊かな人 (o/x ?)
有名か豊かかな人 (o/x ?)