Dave, I remember an old mechanic friend talking about pinking. Wikipedia more or less confirms what he explained to me.
Wiki uses the term "pockets" of fuel/air bringing it about when ignited.
Glowing carbon deposits, sharp edges of newly ground valves,anything that could retain a combustible glow brings about pre-ignition....... a different thing to Pinking.
A more complete combustion of each inlet charge of fuel should happen with added HHO. A less tendency for unburnt fuel pockets to occur.
You can only imagine the enormous loading on cylinder components if combustion comes about early during the compression stroke.
I can understand why Bob Lazar & others do not entertain using Hydrogen in diesel engines. You are in not much of a position to determine the point of ignition with the diesels principle over the spark plug. It has crossed my mind to reduce compression ratio if need be...... I then have to consider the possible problems just mentioned by you yourself.
Marshall.
P.S. Things also seem to be very quiet for Bob Lazar at the moment. His Hydrogen section has had no update since February.
http://www.switch2hydrogen.com/