I've had four games where I was either doused along the long or directly by the arsonist but somehow did not die during his first ignite, I've actually talked to two arsonist players when this happened (It was some game's where we ended up being some of the last townies left in the square, 1 V 1 I recall). I've been told from their perspective that I am still doused, they ignited and somehow I didn't die. We both were quite confused but a subsequent igniting fixed the issue.
So I somehow end up immune to the first igniting by arsonist, it hasn't happened consistently to my knowledge but the number of games where there is a arsonist and I get ignited before they either die or I die from other means are staggered out so much I can't keep track if it's a consistent bug I'm experiencing.