Oh man I should have done it on CO OP then :(
Well I just did all the audio logs on the Halo 3 ODST easy playlist. I am going to restart my xbox and then see if the normal campaign was affected.Hmmm.... I haven't found all the audio logs yet, I was getting them casually while playing through Co-Op with someone who never played ODST. In my experience, when I tried playing again all my audio-logs were gone and I had to find them all over ago. Is this not normal? (I know its not normal for ODST, but things being messed up and not acting as they originally did is the norm for MCC)
Well it was affected. All audio logs unlocked permanently and all city ambiance ruined... was it worth the achievements and gamerscore? I don't think so :(
I wish I saw this thread sooner.
I played co-op (split screen, not sure if online makes a difference) a few weeks ago and we split up the campaign in like 3 sessions lasting a few hours each. The whole audio log thing reset (achievements unlocked) but so did our story progress. Every time we wanted to resume it started from the beginning when you are stuck in the drop pod hanging on the side of a building. Thankfully the game kept track of what levels we beat and what difficulty so we just worked around this reset but loading the level we were supposed to be on.
I know you cannot undo your audio log progress but maybe launching co-op might help if you ever play with someone and want that ambiance again. I hope its there since you don't have anything to lose and might be able to regain something you liked about the game and its atmosphere. The downside is the disjointed story progression if you and who ever you play with don't finish everything in one sitting.