I was just in a game (caa) where an arsonist doused the mayor night 1. he claimed arsonist in daytime so we didn't lynch him because arsonist has to wait a night before igniting or else they kill them self. the next night he ignited, killed the mayor, and didn't die. sure he could have been healed by doctor or potion master, but if so they would have died with the mayor so it wasn't that. I think this was a bug unless they changed the game so that arsonist no longer has to clean them self before igniting. But as far as i know its always been that way. also in the role card it says "if you take no action you will attempt to clean the gasoline off yourself. I'll attach images on imgur.
https://imgur.com/a/M31pQ6H