: Yes, that's what we're discussing. It sounds like a great option.

Sure. I'd be all for that :P
But I offered a 'best of both worlds' idea. If 343 put them in because they want to let the people who want multiplayer achievements have multiplayer achievements, then taking them back out would be off the table. So, compromise - split playlist. Give those players back their MP achievements, and let the people whose games are ruined by those players play without worrying about those players ruining their games. Win win. The drawback, as you say, is dividing the player base - but no more than existing playlist preferences do; and the other options each have their drawbacks, their acceptability of course depending on who you talk to.

But hey, just an idea. Probably even already considered for all we know.