A lot of people fall back on old knowledge that was relevant years ago.
The yesteryear problems of diesel engines are almost completely gone.
Fuel gelling is of no concern in these machines unless you live in northern Alaska at -60. If you live in an area where winter conditions apply, your local fuel is treated before it hits the gas station. There is summer fuel, and winter fuel, all over North America. Winter fuel is, you guessed it, formulated specifically for cold weather operation.
Moisture, again, on these machines, I doubt it would ever become an issue. Your only holding 25 liters of fuel here. We are not talking about 1,000 liters. If you stored your tractor for years without so much as looking at it, with lots of empty space in the fuel tank, sure, you might have a moisture issue. If you burn your fuel on even a remotely regular basis, no worries.
I do not run any additives in my X740, and I likely never will. With the diesel fuel we get today, and considering how small these machines are, additives are dollar bills coming out of the exhaust. Someone mentioned the diesels leave soot on the hood. I have just under 30 hours on my X740, with not one wash done yet. I have absolutely zero soot on my hood where my exhaust comes out underneath. It gives one puff of black at start up, and that is it. They burn clean.
Let us all remember these are 24HP garden tractors, and nothing more. Enjoy your machine, whatever you have, instead of worrying about what may or may not ever happen to it.