In general, I agree with antlers and others who say "why not?" - if it's good for the kid, let him wear the letter since that's where the kid's parents have put this situation. Any happiness or motivation of any kind he gets from wearing it will not diminish the significance of the earned letters being worn by the athletes. People understand this stuff.
This reminds me that somewhere around here there is a box with HS and college varsity sport letters that got removed from old jackets. Aside from a few nice memory recalls, those things are about worthless except when my grandkids root through that stuff for fun and ask about those days. Where do we place and live our emphases?
There is one comment in that article that DOES bother me a bit - has nothing to do with this kid's situation - but does have to do with recognition of excellence in our midst. More and more over the years I have seen trophies/lcertificates/letters/ribbons/etc. handed out will-nilly for "participation". Where did we lose it? Isn't patricipation a basic reason why folks engage team sports, etc.? So, why did we start handing out rewards for showing up?
Not simply in sports - but overall - how can it make sense to compromise recognition of excellent performance and great effort on the part of some people because sensistive feelings might arise on the part of those who were not so good and didn't get praised? This is life. None of us are good at everything, some are good at some things - and we all participated.
Hey - give me a "Z".
