It's often said (about the 'dregs') and as much as I would avoid running a tank down I'm not entirely sure it is particularly correct.
Just think about it for a moment - where is the lifter pump taking its fuel from? It ain't the top of the tank!! So wherever it is pulling the fuel from, that's where it is pulling the fuel from, and if the fuel is below that, then it's run out of fuel!
(I'm gonna have to run my own tank down soon, to replace that blessed seal on top of the tank, which seems to be seeping... so I hope that is true!)
It's not so much that you 'should never' run out of diesel, but you'll likely have to bleed the lines before it will start up again. Not always necessary, if you are lucky, I ran a Renault Magnum 450 [Articulated unit - 12 litre, 6 cyl] dry once (I was trying to make it back to a bunker to fill up the 1000 litres of tanks!) and (thank god!) it started up again once I got a bit of fuel back into it, from a petrol station I happened to judder to a halt 100 yards away from! (my luck exceeded my stupidity that day! Better than the other way around!)
'In the old days' you'd just slacken off the nuts holding the injection pipes in place, and let the lines bleed through the threads, and tighten back up once started. But with
, etc., there are other means. If you read the handbook, it should describe how to bleed off your car, if you get caught in that situation. There will be some yellow coloured tap thing you'll have to turn open to do it, I expect.