Unfortunately it suffers greatly - to a ridiculous level, in some places - from that ugliest kind of grafitti, convoluted "tags" made in single-stroke black ink
I'm not sure if that is the case everywhere but in Brazil people even have a separate name for that (pichação), to separate it from grafitti (which evokes some form of art)
It is truly staggering the amount of pichação you see in São Paulo. Google "pichação são paulo" to have some idea
Here's an example: https://jpimg.com.br/uploads/2017/04/3914518869-pichacao-em-...