We were there a couple days ago. We go at least once every time we visit NYC.
And Kenny was in rare form on our most recent visit. Some hipster douche was standing around being fussy waiting for his date to arrive. Started asking too many questions. Then, he asked a customer sitting at the bar to move over.
At that point, Kenny snapped on him. Told him to fuck off and that Shopsin's "isn't the place for you." The hipster protested maybe not knowing that Kenny was the boss. Hipster said that he was going to stay because his date really wanted to eat at Shopsin's. Kenny said "she can stay, but you can't." Threw him out viciously.
We laughed the rest of the day over that scene. We congratulated Kenny for trying to keep his place hipster douche free.
On my last visit, about a month ago, I saw a man denied a table because rather than sit down when asked, he continued to stand around asking loudly whether the place was serving food (despite being told twice that it was). So yes, there are rules, and you might run afoul of them. But you have to transgress - it's not arbitrary.