I had a Ber dissapear after a few hours from trading it so there are lots of dupes. Also made an Enigma and it's still there for now...
As for the runewords, I guess it depends how blizzard keeps record of them... If every rune keeps it's ID than the dupes will still have duped ID's so it would be possible during a ruststorm scan to find them and delete them (Although I wonder what if the Jah dissapers from the Enigma? U get 'Empty Ith Ber' or 'Ith Ber Empty'?)... On the other hand if the runeword gets a new ID as a whole than it would explain why the 2 Zerkers did't dissapear (because the Eth added made them get a new ID).
It is also possible (and likely) that both methods are used in which case ALL the items/runes used in making a runeword should be legit in order to last for a lifetime

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Anyone knows how long does a ruststorm scan take? I mean why don't they do it once a week or smth? Even daily?
It's ok that blizzard is focusing on WoW but they should have some staff on D2 just to keep this a hack/dupe free enviroment...