That is a great looking knife Ken. I know most of us here look at vintage knives, and cringe when someone cleans them, let alone modifies one.
Given the info you posted above, I have to say, I don't look at this one the same...
The gentleman is 83 years young, and feels a need for the knife to be modified, because of physical issues ?, so he can more easily use this particular knife.
I think at his age, he has earned the right to make the choice of modifying a knife, even one most would never consider altering. It will probably bring him great enjoyment, to be able to carry a fine knife like this, and at his age ( no disrespect meant ) who knows how much longer he will want, need, or be able to carry a knife.
"Sacrificing" a knife, for a mans enjoyment in his advanced years, is far more important, than one knife. To look at it any other way, would be selfish IMHO. YMMV of course