while high gas prices are not desirable, I have never believed the hype of those who say Iran can have 'catastrophic' impact. There will always be someone else who can step up to fill the oil needs. The incentive to do so will be too high.
Iranian rhetoric is getting high. If they do any of the things they have threatened, be it denial of rights of passage, mining, or open attack, these will be acts of war, and will not be tolerated by the US or our allies. I suspect that FONOPS are already underway.
I agree, that we can't discount the ability of another nations to step in and fill the oil void, but speculators will not be counting on that at the outset, I presume, given the reaction to Katrina. If they fear a gulf-wide war, they would likely price in Saudi disruptions, too.
You're missing the point of the post you are quoting from. If the Straits of Hormuz are blocked, it doesn't just stop Iranian oil, it stops all the oil from all six Persian Gulf oil producers. That's stops the flow of more than half of the world's oil from making it to the international market place.