Well, i tested this dupe in a C1 server and it functioned perfectly.
The thing is, that you get some Karma (being PK is ok). I tested it with 2 machines, not sure if function with only 1.
1) Get some karma points (just to be sure u will drop items when you die)
2) Log in a char. Put all the stuff in the Warehouse, except for the item you want to dupe
3) Walk with the char to a place where there are few ppl
4) Press ALT+F4 and quickly with the other machine log in with the same char.
5) There's a HIGH chance that the same char will be logged at the same time.
6) Kill that char
7) Get the items

Log out
9) Wait a little till it gets logged out, then log in and you will have the same item twice.
Ps: Well, it functioned with Chronicle I (C1) and with 2 machines. Never tested in C2/1 machine.-
Hope it's usefull.
I will be very happy if you take this "Dupping method" as usefull and get my a premium account. (send me a mail to the mail of this user if it's possible).