duping can and has occurred in d2r, but since day 1 i don't think it's possible to temp perm anything (which ultimately is just removing the flag for deletion and exiting before it is reapplied to the items). closing the trade window or taking a waypoint will poof a flagged item in d2r. in d2lod, only items flagged by the ith scanner did that (basically runewords that had the runes removed, but no valid rune combo placed into them yet before leaving game/closing a trade/taking a waypoint).
so i guess if you have a dupe method, you would have to make sure the items either don't clash by their type or never enter the same server together & get flagged without a way to rollback... or figure out another way to get the item not to be destroyed