Meaning:
“不喜” means “to dislike,” “勿” means “don’t,” and “喷,” which literally means “to gush out,” is often used by Chinese netizens to mean “using abusive language to criticize.” People often use this catchphrase as a precaution before they are about to share their opinion online. It can be translated as “If you don’t like my opinion, please don’t use abusive language toward me.”
Example:
A: 你总是潜水，今天也来说说这件事情你怎么看。
Nǐ zǒngshì qiánshuǐ，jīntiān yě lái shuōshuo zhèjiàn shìqíng nǐ zěnme kàn。
You never joined our online discussion. Now tell us what you think of the topic we are talking about.
B: 好吧。下面是我对这件事的一点分析，大家可以讨论，不喜勿喷。
Hǎo ba。Xiàmiàn shì wǒ duì zhèjiàn shì de yīdiǎn fènxī，dàjiā kěyǐ tǎolùn，bùxǐ wùpēn。
Okay. The following is my analysis of this issue and it’s open to discussion. If you don’t like my point, please don’t use abusive language toward me.