Many delis are Jewish. He's saying that whenever he sees buildings named after people, he's in a Jewish neighborhood. In context, it plays into nasty stereotypes about Jews being obsessed with money.

I don't think that was the meaning of the gp post. If you're traveling, names on buildings or businesses tend to reflect the population of that area. Thus, if you're in an area with a large Jewish population, you can expect to see buildings/businesses that reflect that too. Antisemitism is a real issue, but this is just not it. I am Jewish by the way, if that matters.

The post didn't say "when I see a lot of jewish names on buildings I know I'm in a Jewish neighborhood," it said "when I'm in a neighborhood with a lot of names on the buildings I know I'm in a Jewish neighborhood" (both paraphrases to keep the dogwhistly deli->jewish link clear). The implication that Jewish people are uniquely interested in showing off their money and status through naming rights donations seems pretty blatant to me.

Ok, interesting. I would usually be willing to give much more benefit of the doubt, but given how unnecessary the comment seemed to the rest of the post, I guess the obvious conclusion is a dog whistle.