Was her work obscene or likely to provoke violent reactions from reasonable people? No. It was the ancient art of calligraphy which Xu Zi began learning from her grandfather when she was a girl. She was asked to leave because a Parks Enforcement Patrol officer, applying a police order, determined that Xu Zi’s work was not art.
Had she drawn flowers or some other picture near the lettering, she could have stayed in the park, but she didn’t like the idea of the government dictating what kind of art she could do. Our Founding Fathers worried about that kind of stuff too, which is why they wrote the Bill of Rights.
This clearly contravenes the court's decision, which says:
Furthermore, written and visual expression do not always allow for neat separation: words may form part of a work of art, and images may convey messages and stories. As appellants point out, Chinese characters are both narrative and pictorial representations. Nahuatl, a language used by Aztec peoples in Central America, also incorporates pictures in its written language. Visual artwork is as much an embodiment of the artist's expression as is a written text, and the two cannot always be readily distinguished.
I'm not sure what style of calligraphy this was — but if anything, calligraphy is even more clearly protected, because it's written language! The issue the court is grappling with in this opinion excerpt — whether rather bland paintings being sold can actually be considered expression — is likely a nonissue in this case.
I had my own recent experience with NYPD and free speech, which I'll detail soon. But Xu Zi's experience is even more clear. It's just another sign that there is no longer such a thing as public space, at least not anywhere that matters. This lack of physical public space is a large part of the reason why I think advocating for a free and open Internet is so important. Unfortunately it won't substitute for physical space, but if it's the best we have, we better keep it.