2-32-10 doesn't say if a nonplayer comes onto the field during the down it isn't a nonplayer foul. Check Case Book 9.6 Comment Table. "Nonplayer enters during down - Basic spot (nonplayer, unless PSK enforcement applies)." So unless PSK enforcement applies, it's treated as a nonplayer foul and the basic spot is the succeeding spot.
OK, so reading carefully, I think that I am right, and wrong, but in the end correct. Maybe we both are. Bear with me, and tell me if I am still thinking wrong.
I still still maintain that it is not nonplayer foul. 2.32.10 A nonplayer is ... a substitute ... who does not participate... If he isn't a nonplayer, it cannot be a nonplayer foul. (Maybe I am wrong, but I don't think so.)
9.6.4a Illegal participation
live ball, basic spot Not previous spot. I was wrong here the first time.
So what's the basic spot? 10.4.4 Where the related run ends.
In the previous discussion, if R returns the punt for a TD, an Illegal Substitution foul would be a nonplayer foul enforced from the succeeding spot, 5 yards on the PAT or KO.
If R returns the punt for a TD an Illegal Participation foul would be a live ball foul enforced from the basic spot under the all but one principle. Which is going to be 15 yards walked off from where the illegal participation occurred, nullifying the TD.
If we have Illegal Participation on A/R on a TD play we are not enforcing that on the Try of KO.
Maybe we're just using different thoughts to get to the same place.