They touch on one of the bad things about lugging in the link given but don't explain it all the way.
When the engine is at low RPM, oil pressure is lower, so less 'protection' for the big ends / bottom end (but as long as the oil 'film pressure' isn't broken, then it is OK).
If at low RPM, and lugging, and then you get detonations, then the massive overpressures will keep banging the big-end bearing shells together, and it won't be too long before you get bottom-end failure.
As detonation is more likely at high engine load (including lugging), as well as cheaper (lower octane) fuels, as well as a hotter engine from a grille block, it makes sense to be very careful!.
P.S. Look at my gaslog - since I got the SuperMID I have discovered the advantages of lower RPM driving. I hope my bottom end lasts!
P.P.S. Lug_Nut - your engine, being diesel, is better suited to lugging anyway - they are stronger, designed to work at lower RPM (and much heavier loads), and, the way fuel burns in a diesel is closer to detonation anyway!.
__________________ Team GasMisers5 - #1 for first three rounds of the original GS Fuel Economy Challenge
Miles displaced by e-bike since 1 Jan 2008: 62.6 (0 kWh used)