Actually, in the initial environment, using 96,97 for the unprovoked D,C (instead of 95, 96) will be more successful. Like O, but unlike the first afterparty, this "late afterparty" (LA) will beat I in an environment of mostly I (score against I for last 6 turns: I gets 18, afterparty gets 16, O gets 21, and LA gets 20). It will also beat O in an environment of mostly it and O (against LA, LA scores 21 and O scores 14; against O, LA scores 14 and O scores 15. So if the environment has more than 1/8 LA, then LA is winning. From the above, if O and LA start out small and equal in an I-dominated environment, as I disappears LA will be around 40%, easily enough to come back and pass O). LA will lose to O in a strongly O-dominated environment , while the original version will win (Afterparty scores 17 against O, above O's mirror-score of 15); but since that situation should never arise, I think that LA has the best chance of coming to dominate the environment. In fact, in an environment which started out I-favorable and with both O and both forms of afterparty, original afterparty's only effect would be to hasten LA's win by parasitizing O.

(Edited; I'd originally used the 3,5,0,1 payoff matrix instead of 4,7,0,1)

Hmmm, for some reason I'd read that as D,D.

I still think it makes more sense to group 96 in with 97-100, though, as a turn where it only plays C if all matches so far have agreed. If 1-94 are all mutual C, then on 95 it plays D and opponent plays C, I'd think it should play D the rest of the way instead of going with C on 96 and then D on 97-100.