I did some more research in my own collection and have actually found several LP's that appear to have been affected by the dreaded "misting" effect. After checking dozens of records I first noticed it on my black copy of Porcupine Tree's "Moonloop" (I also own a white one, but it's probably much harder to spot on that), these originally came in a purple PVC inner sleeve , packed in a mylar resealable outer sleeve. I put the record in a Nagaoka 102 poly inner after purchase, and stored that in the mylar outer sleave, together with the original purple PVC sleeve.
The record has a vague but noticeable "spotty" appearance, with a hazy line pattern radiating all over the disc. The sounds is not affected by it at this point, so it is not clear if the "damage"occured after I repackaged it, or during the time it was in direct contact with the PVC inner sleeve. I bought the record at a gig, so it could very well have been stored this way for quite some time.
A few things I noticed about the purple inner sleeve:
It seems a lot softer than the "regular" PVC outer sleeves, and while it smells similar, the "PVC smell" on the purple sleeve is A LOT stronger than most of those clear outer sleeves.
With this in mind I immediately thought of those "Simply vinyl" outer sleeves (with the flap and the round sticker to keep them closed), which are also a lot softer than other outer sleeves, so I decided to check those next.
When pulling the first "Simply vinyl" release from my shelves, I was greeted by the same smell that the purpe "moonloop" sleeve had, but found no "misting" on the disc, but further inspection revealed that one of my older "Simply vinyl" releases: Metallica's "Black album" had actually been affected. (Again only visually, there's no hiss)
I have also found several other records with a slight, purely visible misting effect in other situations where they were originally packaged with the soft, almost rubbery PVC as an INNER sleeve, the Metallica album appears to be the only album that was affected right through a cardboard gatefold and a poly lined inner sleeve, but I have noticed that that distinct PVC smell actually carries over to albums (not just the sleeves) standing next to the ones packed in them.
I also found that quite a few of those softer PVC sleeves had stuck to the cardboard gatefolds and were actually pretty hard to remove without damaging anything.
While my experience with this "misting" effect is still very limited compared to the less fortunate people in this thread (Thankfully no audible damage yet), I have decided to get rid of all the PVC on my record shelves. I spent the afternoon getting ALL of my albums out of their PVC outer sleeves, and looking for alternatives for those that came in PVC inner sleeves. Maybe I am overreacting, but at this point I'd rather be safe than sorry. Since i only own a few 100 records I'll probably invest in some "poly" outers in the near future, but for the time being i'll keep them "naked".