In a thread that has since been deleted from social media forum Hupu, mainlanders looking to visit the city asked how to dress and behave so that they won't be attacked by Hongkongers.
Suggestions included ways to disguise a mainland accent, such as trying to speak with a Taiwanese accent, swearing often in Cantonese, or speaking a mixture of Cantonese and English to sound more local. Other users encouraged visitors to make use of Hong Kong's current political sentiments by loudly criticising Chief Executive Leung Chun-ying.
While some netizens defended Hongkongers and claimed the city was open and friendly to tourists, others warned against visiting areas like Tuen Mun where recent protests against mainlanders have led to arrests and violence.
There may be good reason for such recommendations and fear over attacks. Sunday's march in Yuen Long resulted in 38 arrests after hundreds of people gathered to protest against mainland traders. Two teens - aged 13 and 16 - were among those arrested.
Police reported that some activists were found carrying "homemade pepper spray" in the form of a chilli oil mixture.
Police estimate an additional 400 marchers were involved in a counter-protest at the site, which led to clashes between the two sides. When violence broke out, the police took action, according to Yuen Long deputy district commander Kerry Carew.
"Police discharged 21 bursts of pepper spray," Carew said. "Other officers used batons to strike and subdue the protesters."