There have been a lot of good comments in the last few posts. Some are over simplified. Some are over complicated.
As for the football player in question, and the affect it has on your son's chances, it is true that it depends where his appointment is charged. But it's not that simple.
1. Approximately 50% of all appointments AREN'T CHARGED TO ANYONE. Yup, that's correct. All of those national pool appointments.... They aren't charged to anyone. While the federal law says that a MOC can have no more than 5 cadets at the academy at one time, CHARGED TO THEM, in theory they could have 30 cadets from their district with 25 of them coming off of the national pool. Those DON'T COUNT towards the MOC. They aren't charged to him/her.
2. As mentioned, an LOA is SIMILAR. They CAN be charged to a MOC's slot, but they don't have to be. An LOA usually comes off of that 50% that aren't charged to anyone. It simply says in an LOA; "Must Have a Nomination". They can be #10 on the MOC's list. Doesn't matter. An LOA can be just like the national pool. NOT CHARGED. Matter of fact; MOST MOC's if they see an individual with an LOA, they PURPOSELY give them a nomination at the BOTTOM of their list. This way they still get their appointment, but they'll rank their list so their #1 nominee ALSO RECEIVES an appointment. (Most MOCs know how to play the game).
3. As for people speaking of getting a "Superintendent" nomination. That's for people who CAN'T or DON'T get a nomination from ANY OTHER PLACE, but the academy really want them. (Not just athletes). In that case, that too has no affect on the candidates who did get a MOC nomination and are competing.
4. As mentioned, Signing Day for academy IC sports means absolutely nothing. It's not contractual and it doesn't actually commit the athlete to anything. But because the academy recognizes that most athlete/applicants have no idea what athletics at the academy means, they intentionally do things like Signing Day because it's something the athlete can understand. And it gives them the "STATUS and KUDOS" at their local high school of being a "Recruited Athlete". But as has been mentioned, the athlete can change his/her mind all the way up to BCT and go to another school. They could get to BCT and decide to be just a cadet and NOT play sports. The coach, especially in football, will cut approximately 50% of the "Freshmen Football" players during the first season. So being a recruited athlete at the academy have very little in common with being a recruited athlete at a traditional school.
So in a nutshell, yes, an athlete can affect the chances of a non-athlete candidate. But it is extremely slim and rare. The ONLY way is if the athlete individual received their appointment and it was CHARGED to their MOC nomination. Any other way has no affect on your son or any other applicant. (Other than the TOTAL count coming from the national pool). Case in Point. My son was a recruited athlete. He also had a Presidential Nomination. He had his entire application completed in July. He RECEIVED an Appointment at the end of October using his Presidential. Now; being he was an recruited athlete, does that mean he may have taken the spot away from another individual with a Presidential Nomination. Very unlikely. Because most appointments aren't done until much later than October. In my son's case, he actually received his appointment PRIOR to being recruited and PRIOR to getting a MOC nomination. Matter of fact, he contacted our Representative and Senators and told them to NOT interview him and to NOT give him a nomination; because he already had an appointment. This way, the MOC's could give a nomination to ANOTHER candidate and it would increase their appointees that year. Point is; just because my son was a recruited athlete, doesn't mean he was "Less Qualified" than a non-recruited athlete. Like I said, my son received an APPOINTMENT PRIOR to being recruited or getting a MOC nomination. He was going to receive an appointment pretty much no matter what. Without knowing the recruited athlete in question, who's to say he wasn't also a 4.0gpa student with 30+ ACT. Captain of 2 varsity sports. In the IB Program or All AP classes. With 300 hours of volunteer time. Vice President of his class. Ranked #1-#5 in his class. I didn't bring up my son much when he was at the academy, but he graduated 3 years ago, so I don't mind mentioning it. He was a recruited athletes, Yes.... But he was also the candidate who received an appointment WITHOUT the need of athletics. He was the 4.0gpa, 30+ ACT, #1 ranked, IB Class, class officer, etc. student.
So yes, maybe this recruited football player might bump someone from receiving an appointment. But maybe they "Still Deserve it". Just because an individual is an athlete doesn't mean they are automatically "Less Qualified" than non-Athletes. It doesn't mean they are all "Dumb Jocks". I know a LOT of academy athletes; recruited and non; who graduated at the top of their class. BOTH High School and the academy. I know a LOT of these cadets who got accepted to grad school, med school, PhD programs, etc. There are a LOT OF PARENTS on this forum who's cadet played high school AND ACADEMY SPORTS, and they also had the 3.9+GPA, 30ACT, etc... I will not argue that there is indeed SOME athletes who get to the academy with less than Stellar academics. But they DO meet the minimum requirements, and 99% of the time, they had a nomination and got selected in the national pool or LOA that didn't have a significant affect on those competing for the "CHARGED SLOTS". So yes, some applicants can be affected, but it's very slim.