It's not a western dog whistle, but rather a Russian one.
Edit: Also, I don't really know whether Kenarov is in any way Jewish but it's not hard for me to imagine someone using the term satirically but not intending to (at least, not strongly) evoke its antisemitic aspect. I don't think that really works in English and aimed at a Western audience but people do irony-recycle the old slogan tropes quite a bit and it's a linguistic theme throughout the piece.
The ideological terms where picked fairly carefully with an eye towards 'ideological soundness' and had multiple purposes. 'Rootless cosmopolitan' was an antisemitic dogwhistle, it was also part of a deliberate effort to shift to a more Russia-centric Soviet ideology. In a way it was also a Russian dogwhistle so tptacek was kind of right after all, completing the pedanticircle.
I regret (and did even at the time) using the words "dancing around" --- I was just waking up (let's not discuss the unhealthiness of "commenting on HN" being one of the first things I did after regaining consciousness) and even as I wrote it was thinking "this conveys more intentionality than I mean to".
So for that bit, I apologize! People still should aggressively avoid the term. I only saw this thread because I've been on a sort of comment bigotry scavenger hunt with "rootless cosmopolitan" as one of the items.
I wouldn't casually use it in English, though, precisely for the reasons you outline.
It was also quite informative to learn about this phrase and its nuances.
Thomas was asserting that "rootless cosmopolitan" was an antisemitic slur that Vektorceraptor deliberately applied to Kenarov. I asserted that the knowledge and usage of that expression is not nearly as universal as Thomas claimed. Thomas clarified that it's a Russian dog whistle.
I've just finished reading the essay you linked there. How does it fit in this discussion?