Yeah, it definitely isn't. High compression engines will pre-ignite with low octane, that's what the pinging is. That will eventually lead to knocking and then you're screwed.
C3 may have to correct me on this but I believe octane raises the flash point of gasoline so it doesn't ignite from the heat caused by compression, which is why diesel fuel doesn't have octane.... At least that's how I understand it.
You are correct to higher the octane rating the more it resist ignition. Diesel is rated in cetane the higher the rating the shorter the ignition delay and the more complete fuel burn