Then why not just machine them to 1.59 mm? I assume if that's really the sweet spot to make the geometric tricks work, it would be well known abroad and foreign blade manufacturs would just . . . make them the right size regardless of which system of measurement they were using. Machining can probably go even more precise than that, since you did say "slightly less." I actually looked it up. It seems machines can have a tolerance level(margin of error, basically) between 0.1 mm to 0.002 mm. So a low-end machine wouldn't be accurate enough, but just a mid-range machine could give you a spread of 1.58 to 1.6, both .8 closer to the sweet spot than 1.5.
What you quoted was me, not Geeky.
The kerf should be as close as you can get it to the smallest measurement that you are likely to use. Or more specifically, no more than double the smallest. Most cuts in carpentry are going to be as close to a 1/16 of an inch as you can get, so the kerf should match. 1.59 mm is not going to be a useful, quick measurement when translating linear distance of the measurement of the cut. You could do it with 1.5 mm with a kerf of that width. (In the same way, occasionally you'll need 1/32 in carpentry, and eyeballing the middle of the blade is usually OK--though harder for someone like me with bad depth perception. But then, I can't make furniture precise enough for that to matter anyway.)
Setting up for mass production, this wouldn't matter so much. You'd pull out a micrometer and set it to exactly what you needed, with stop, complete with an exact inclusion of the exact kerf you have on the saw. My dad does that occasionally for key measurements in really tight pieces. That's obviously a lot slower than being able to consistently eyeball the blade. You can't do that every cut as a carpenter if you want to eat, though.
As I said before, this is all at the margins, though. Give me nothing but metric to use and an 1/16th kerf, I could make the piece. It would just take longer, with more mistakes, and probably wouldn't be quite as fine as I'd make otherwise. Wood's got a certain amount of give and take anyway. What my dad would make under the same conditions would be better than what I'd make without the handicap, but not as good as what he'd make without it.
Give him a 1.5 mm kerf and nothing but metric, he'd adapt. He'd get back to the same quality as he has now, eventually. The point is that nothing would be gained except others would have the satisfaction of knowing they'd forced metric on someone. This isn't like chemistry, where there is a solid, positive, compelling reason for the switch.
Edited: Of course you can make a 1.59 mm blade. We've already got that. You can also make a 1.5 mm blade, which would be a heck of a lot more convenient for someone using metric otherwise. The difficulty is that blades are surprisingly fine in how they work, such that changing the width that much changes their manufacturing for a given finesse of cut. Some of the diamond tip blades are already expensive. Granted, nothing compared to the cost of the saw, but the saw lasts a lot longer, Again, could be made to work, but there isn't any appreciable gain for switching, and carpenters don't make a fortune (i.e. already have fairly tight economic margins). Now, a 2 mm kerf might be pretty amazing in some cases.