I can't find where I was reading about it, but my recollection is that a small number of lyrics on Midnight Oil were considered "unintelligible" during the remastering, and those specific lines were dubbed over with fresh takes from Pete. It's certainly not rampant. I think I noticed it in one place, and I'm too lazy to pull out my CD and check.
I didn't buy the remastered version of Diesel. I did buy the remastered versions of everything pre-Diesel. I don't think the remaster was necessary, and I don't think it constitutes an improvement.
I just realised I've never listened to the remaster of Blue Sky Mining. I might pull up Spotify and do that now, just for my own amusement.
Incidentally, my googling just turned up some forum threads on the "Culture Factory" re-issues that were mentioned on the list recently - apparently the "remastering" is awful. Can't say I'm shocked.