Another potential Illegal Participation play

[The Roamin' Umpire]

NFHS Rules (though I'd be curious to see NCAA as well):

PLAY: K 4/10 @ R-35. Punt formation, with player K99 lined up about 2 yards from the sideline. At the snap, K99 dodges around his defender by going OOB. He runs up the sideline (OOB the whole way), while the kick is made cleanly, hits near the sideline around the R-10 and bounces towards the end zone. K99 beats the ball there and is standing OOB at the R-1 when he bats the ball.

I believe this is a legal play. I believe it probably SHOULDN'T be, but I can't think of a reason why we'd have a flag. Thoughts?