Um.... acetone evaporates. I got two shrunken heads (intentionally) that are not melty or gloopy... I certainly would not recommend using acetone on any hard plastic, but a quick wipe of a vinyl doll's face with running water never does ANY of my numerous 1/6th dolls any harm.
Okay, acetone does melt the surface slightly of hard plastic, but it evaporates.
I honestly remember those pictures were from someone who used a thinner. I shall use my google-fu as I slowly type this...
Found it:
http://www.junkyspot.com/OBITSU/forums/index.php?showtopic=8079&hl="So let's think what other stuff I got in my car...Oh...thinner, lets read the label then- To use for paint thinning and removing paint from most surfeses. Great, lets try it on one tiny limb...finally somthing that works, all the blue (oil) paint went off. Yay....lets wash the hole doll body then (bad, verry bad idea) All the body parts are nice and clean (exept some tuff blue spots)Lets wash all the leftover from the thinner (I most have left some mad.gif )"
So yeah, that pic wasn't a result of acetone.