Every long-lived civilization has some form of venting mechanism for the frustrations incurred by daily life in a stratified society. One form, the “inversion festival”, has remained popular throughout the history of Western society under a variety of names: Saturnalia, the Feast of Fools, Mardi Gras, Halloween…
The Noospherists took the meme, like many others, to its’ exaggerated logical extent. Catharsistalia is held on the last day of the Centauran year, once a decade it gets prolonged to the full 19-day month. During this time there is only one rule, “nothing permanent,” no deaths, no ruinous financial damage, no conceptions. Whatever happens during Catharsistalia, stays there. By custom the civil police and even the Bureau of Memetic Health cannot do anything about the various petty thefts, fights, orgies, or satirical rites of Death worship that may occur during the festival. That said, some token effort at a disguise is customary, most of the costumes worn won’t stop a serious investigation if you commit murder but it’s the principle of the thing.
Many local governments will organize events to limit the damage, especially for the decennial fests. The most common involve designating a park or arcology block as the fair grounds. Residences and storefronts in the area secret away anything of value and lay out cheap snacks or toys someplace they can easily be grabbed. Some places will shell out for a security drone programmed to give chase when something is “stolen” but let them go. Other areas are set up as fighting arenas, in disciplines ranging from wrestling to swordfights with live steel, medichines making even decapitation survivable. Still other spaces are set aside for parties, generally with STD and contraceptive screenings ahead of time. And usually there’s a small space for the minority of pre-pubescents in the population to have fun safely.
Some reform movements, particularly within fringe sects of the Noospherist Church, try to discourage or ban Catharsistalia. Which invariably results in the decennial festival happening early, on their property, courtesy of the local Kitsune skulk.