Actually, it was the “there” (hidden there in a crowd) that confused me into thinking it was Danny who was hidden.
I agree completely with wolfpup, but I’d quibble that “I drove here in mine own car” is the more correct.
Maybe next time I’ll see if I can quote things correctly.:o
getting it done right on my own.
If you’re into extremely archaic usage, sure.
Since the OP was based on a misquote, in the absence of which the question answers itself…
I see little difference between archaism and pedantry. 
Is no one going to quibble about “Heaven Forbid” vs “Heaven Forfend”? It’s like I don’t even know you people anymore!!!
Indeed, the OP’s title begged the question.
I won’t exchange insults (and in any event, I have multiple objective measures of my competency and fluency in the English language that act as Teflon to your insults), but you perhaps inadvertently moved the goalposts with your car example, which is not parallel to the one we have been arguing over. Try this instead:
*I drove here in his car.
I drove here in his own car.*
You can’t use “own” the way it is used in the second sentence, just as you can’t use it the way it was said to be used in the misquoted OP. Your error, again, was in doubling down by continuing to endorse that usage even after it was revealed to be an error in transcription.
ETA: Again, this is very reminiscent of reflexive verbs in French. You can use this sense of “own” in the following ways:
I…my own
He…his own
She…her own
You…your own
We…our own
They…their own
You can’t mix and match.
This is helpful, but I think it’s just showing why the sentence in the misquoted OP seemed wrong to some people upon first reading because they misparsed it as analogous to your example above (and therefore incorrect). In fact, the misquoted OP is perfectly fine per UDS’s analysis in the second post.
It’s notable that there’s variation among readers as to whether it’s jarring or not - to me, and to some others, the misquoted OP was completely unremarkable good English, I naturally parsed it according to UDS’s analysis the first time I read it (even without context) and at first I wondered what the problem was. I had to “work” on re-parsing it to realize what other people were seeing as a mistake.
I’m not seeing why you can’t. The way I use English (which is admittedly idiosyncratic) “own” after a possessive pronoun is an intensifier of that pronoun. Regardless of prior pronouns.
This may be a regional and/or age thing.
No. You have a participial phrase containing an adverbial prepositional phrase: “hidden there in the crowd of his own adversaries”. Regardless of what else is in the sentence, this verbiage can only be used (correctly) in the case where the person hidden is in amongst their adversaries (and male, for that matter). If something else is meant, you absolutely have to get rid of the word “own”.
ETA: To greatly simplify, while keeping the intended meaning from the OP, do you believe it would be grammatically correct to write “I was hidden there in the crowd of his own adversaries”? Because I absolutely do not.
I had no trouble understanding the sentence when I read it in the print edition, but I had to pause when I read the misquoted one. I think “own” here might imply that the enemies are close to the other person, not to the “me”. Though the two sentences are logically equivalent, they may not be equivalent in their implications.
BTW questions on grammar in the New Yorker seem to me to be absolutely appropriate here, just like a question about the violation of a physical law would be. I haven’t noticed any, at least not since That Woman left.
Ok, then maybe I misunderstood your prior post. Are you saying that this is wrong:
He did not see X hidden in his own Y.
In my dialect of (British) English, this is fine. The presence of “own” might connote a difference of emphasis (or not) depending what X and Y are and upon context. I don’t have a good enough feel for US English to judge whether this is a UK/US difference, but in any case this aspect is not a question of grammatical analysis, it’s just colloquial usage. There’s no “absolutely” here.
I have no problem with that sentence, depending on what it means. Let’s clarify by changing the subject “He” to “Z”:
(1) Z did not see X hidden in his own Y.
This is fine if Y is something X owns or which is connected to X. But in the (distorted version presented in the) OP, what it meant was:
(2) Z did not see X hidden in Z’s Y.
And it is nonstandard English to write sentence 1 if your intended meaning is that in sentence 2.
But you only get “distortion” if you mis-parse the sentence.
If you would agree that there is no problem with:
(a) He did not see the flag hidden among his own adversaries
then there is likewise no grammatical problem with
(b) He did not see me hidden among his own adversaries
That’s clever, I grant you. Not bad. But there is no risk that “flag” could be the antecedent for “his”. And I would still question the use of “own” in the flag sentence, even though it is not as egregious. Maybe if there were a broader context in the passage in which there could plausibly be other people’s adversaries under discussion.
But (b) is still terrible.
This reminds me of how many people use “himself” and “myself” as synonyms for “him” and “me”, respectively. This usage too is nonstandard, but it is getting common enough that it may eventually be seen as acceptable in writing (shudder). Not yet though.
I’m not sure what you mean, I’m not trying to be clever, just to drill down to what your point of contention is with the sentence.
So ultimately you do agree with UDS’s initial analysis in post 2 that, if parsed correctly, in principle it’s grammatically fine?
As for the stylistic question - bear in mind that the native speakers here seem to be split on whether the sentence is immediately jarring. Although “own” here is colloquially okay for me, I do agree that it’s superfluous, and the sentence is clearer without, as the New Yorker actually had it. And, ultimately, if around half the people who read the sentence with “own” mis-parse it, then by definition I think that pretty much makes it poor writing.
No. I strenuously disagree with that post.
I see that the discussion has become well advanced on exactly the point I came back here to make. But it’s worth re-emphasizing again because the above declaration is absurd as a context-free absolute.
To be clear, I think we all agree that the wording in the New Yorker is correct and we’re discussing the use of “own” in the misquote. And my example of “I drove here in my own car” in #19 was not intended to be an exact parallel to the OP but just a simple example to refute the allegation that don’t ask made in #18 that “own” changes the meaning of a sentence. In both cases it’s just a possessive determiner that adds emphasis.
I’m with Riemann that the use of “own” in the OP and in his simplified example are both exactly the same and both grammatically correct, as in both cases “his own” refers back to the pronoun “he” and presents no grammatical difficulty:
(1) I waved to him, but he didn’t seem to see me, hidden there in the crowd of his own adversaries.
(2) He did not see me hidden among his own adversaries.
Neither statement can be said to be “terrible” but it all depends on context and intended meaning. As I already said, in (1) the extra word is redundant and perhaps potentially confusing, though I didn’t find it so. But a statement like (2) would be just fine if there was some need for that possessive emphasis. In fact the more jarring part is the semantic one of applying the possessive determiner “own” to a noun like “adversaries”, but that’s a style issue and totally not a grammar issue. There’s certainly nothing wrong with the equivalent construction “He did not recognize me because I was wearing one of his own disguises”.