Profanity, also known as swearing, refers to the use of foul language that is often linked to incivility. In Chinese digital space, the state government actively censors profanity under the rationale of protecting online civility. This study examines the diffusion of profanity in Sina Weibo, one of the largest Chinese social media platforms. The study applied computational methods to reconstruct the cascade networks of swearing and non-swearing posts and analyzed the network diffusion processes based on a set of structural metrics including reposting depth, width, and interlayer width ratios. Findings suggest profanity may influence the process of message diffusion, but this effect was ephemeral. Based on the understanding of diffusion processes of profanity online, this study contends the viral potential of profanity may not be as severe as the regulators claim. The discussion analyzes the extent to which content moderation efforts are necessary for the nurturing of civility online.