Billy,
We have clarification on what "participate" means from 10.5.3 The ball must be live for a player to participate. If the officials don't observe more than five team members during a live ball, then 10-1-6 has not been infringed.
Otherwise, you provide some thought-provoking scenarios.
10.5.3 SITUATION:
A5 has just received his/her fifth foul of the game. A5 (a) is
erroneously permitted to remain in the game for another two minutes before the
scorer realizes the mistake; or (b) leaves the game after the coach is notified of
the disqualification. At the intermission between the third and fourth quarter, A5
reports as a substitute and subsequently enters the game. RULING: In (a), as
soon as the error is discovered, the player is removed from the game, no penalties
are assessed. In (b), A5 will not actually "participate" until the ball becomes live.