My next-door neighbor is a marine guy, out for a few weeks at a time on a (IIRC) fuel tanker.
He said that there is ALREADY a requirement that any ship within 200 miles of any US coastline has to be using #2 diesel instead of bunker oil. Since he works in the Gulf, 99% of the time they are on diesel. He said that the pricing for the heavy sludge was something like $1/gallon... And that the bulk rate for the #2 diesel is like $3 a gallon, obviously MASSIVELY increasing their cost at the many-tons-per-mile that they consume.
HOWEVER - these articles are making a false equivalency. The IMO is requiring "low sulfur FUELS" not "low sulfur DIESEL" as the new order. So it very well may not be actual #2 diesel stocks and other middle-distillates that the ships take. They are already set up with heating systems to boil their fuel so it will even flow, if there is a way to reduce the sulfur in that stuff and not triple (or more) the cost... They will certainly pursue that b/c of the volume they have to utilize!
There's a LOT of hair-on-fire predictions right now, but since so much of the commerce of the globe relies on #2 diesel, I predict the oil industry will have to respond by developing an alternative product for the ships - something they should have been doing already as this is not a new requirement - and the overall market may blip, but not spike like predicted because it WILL crash the world's economy, and that's no good for anyone.