The first Halo I played on Xbox Live legitimately was Halo: Reach. Around August 2010, or 2011. I had actually made my first XBL Account a few months prior, but that's not important (I played most of the Halos by that time btw).
In Halo: Reach's Infection Playlist at that time there was something interesting put into the gameplay: Betrayal. I cannot tell you how many times I've been betrayed by random players in Infection. What's even worse is that you turned into a Zombie after being betrayed (so freaking irritating it's unbelievable). To combat this I stayed away from the other players, and toughed it out on my own. Occasionally I clung to some people if I see they're honorable, and not total pricks from the way they act in the game.
Eventually 343 or Bungie (I forget when Bungie splintered away from Halo) decided to remove Betrayal altogether from Infection at the start of 2011, or 2012 (from what I remember). The quality of the matches literally increased overnight because of the lack of "catering" to the immature/troll players.
Continuing my run online in Reach, 4, and then MCC I didn't really have any positive experiences with Betrayal in any of those games (Custom Games is an exception). It's the usual bs of people killing you for your Power Weapons, Vehicles, or just you getting trolled. When playing with people I know then I guess it's alright.
For Custom Games it's a so-so kind of thing. It's hilarious when you get killed, and when you kill only because you're playing with people you know (usually). Unlike playing in Matchmaking when you're with random people 24/7. And from what I know Betrayal is also a vital component to some gametypes, and maps.
To cut to the chase here's my final OP on Betrayal:
Betrayal should mostly stay out of Matchmaking altogether, but be kept as a toggle-able option in Custom Games.
For the sake of recreating the legacy gameplay for games like Halo 2 in the MCC it should be active for a few Playlists, but not all of them. The same goes for the other games.
The Playlists that are Pro-Betrayal, and Anti-Betrayal should be highly favorable towards Anti-Betrayal: kind of like the ratio being 1/4th Betrayal, and 3/4ths Anti-Betrayal.
I don't want to play Team Slayer with the ominous threat of Betrayal looming over my head all the freaking time, but for a Playlist like Action Sack (if it is ever implemented) it would be alright to have it there I guess.
Anyway what's your OP?