In the recent thread titled Reason for 「のか」 and 「かもしれません」 in 「何を言っているのかわからないかもしれませんけど」, my impression is that saying "何を言っている のか 、分からない" sounds abrupt (and sort of impolite). While I have no idea if this is correct Japanese, I would have said "何を言っている なのか 、分からない". The "な" seems to take the edge out of the straight-up "のか".
The answer to the thread titled 「なん」as a formal, spoken, suffix for questions? mentions the phrase "なのか". But, I can't figure-out if that answer is applicable to my desire to say "何を言っている なのか 、~" instead of just "何を言っている のか 、~". I also found this thread titled What exactly is なの(nano)?. That thread looks relevant to my questions in this thread, did it really only confuses me.
- Is it even possible to say "何を言っている なのか 、分からない"?
- Would saying "なのか" make the sentence less formal?
- Would saying "なのか" make the sentence less aggressive / abrupt? more polite?
- Would saying "なのか" make the sentence sound more feminine?
- Would a native speaker actually ever say "なのか" in this type of sentence in a conversation?