SIWOTI stands for Someone Is Wrong On The Internet. The syndrome was immortalized by this xkcd cartoon. Many Pharyngulites are notorious for suffering from this syndrome and for inflicting the results on others.
Once this syndrome has been triggered, there's not much one can do to stop Pharyngulites from acting on it. They won't let go as long as there is WOTI in sight. For this reason, SIWOTI syndrome has been responsible for some of the longest threads on Pharyngula, and was the major driving force of the Endless Thread in its early days.