Serious Dupe Bug using client/server desynchronization

How to do it: Log in, place an item (or 27 stacks of them) into a chest. Then, you log in with another account, (so you have 2 minecraft windows open), and log into the same server. It kicks you for logging in from another location. The game does not save your client inventory, but saves the server inventory (of the chest), so when you log back in, your inventory will still have the item(s) you have put in the chest, and when you check the chest, the item(s) are still in it, effectively doubling your items.

So yeah, I am going through my list of important bugs, and am trying to report as many as possible. I think this was tried to be fixed in 1.8, but it is still possible. Panda4994 said that it would be possible to fix by having the server save after someone logs in with another account. I think that this was done in 1.8., as it no longer says that you logged out, and are not in tab, but still are able to interact. Here is an example of me doing it: http://prntscr.com/67pjyb

As you can see I logged out, but am still in the game.

I have tried it recently, and it still works, but only after multiple times, and it is much harder to do.

Thanks, Noerdy