David,
My experience with Vincents is exactly the opposite. Carleton Palmer was using Ian Hamilton's piston design, but after racing it for a while the area between the crown and the top ring groove showed distress at the exhaust valve. He lowered the rings and coated the pistons. The life of the pistons trippled and he was able to eventualy get seven addition horsepower out of the engine with no problems. The additional power came from other mods, but the bike got three national championships with excellent reliability. I will say that it has been remarked that the coating in general makes the combustion chamber cooler as the heat should be evacuated in the exhaust, thus allowing for a denser intake charge. I know nothing about Triumph combustion chambers, but the Vincent seems to do OK.
Getting back to the thread, If you work a Comet hard, you are entering an area where you need to do better than stock. The previous owner of my bike used a Specialoid that broke at the wrist pin, breaking the rod. I know that I am being unfair, but I see no reason to run a Specialoid. I think the Omega is fine, but I am not certain that it can do the best job for what NKT267 is doing, particularly if they have stuck in the past. I also think that there is something else going wrong with the engine to cause this failure. I would be curious about the thrust washers in the big end and the interference fit of the liner. The Omegas are only as good as the cylinder. I wonder if all that oil on the head joint has come up the inside of the liner.
Carlton Palmer also found that the wrist pin clearance is too tight for racing. He had Carrilo add a half thou and the heat discoloration and tightness went away. I do not know if this would be an issue on the street.
I do like you comment on the spark plugs. This is easily checked before assembly and your point is well taken.
David