I have now.
Tell me, how is that code used?
Because, and tell me if I am wrong:
I can send NXT from my wallet to any other wallet by inputting ONLY their 18/19/20 digit wallet key.
Anyone that can open their wallet that has that same 18/19/20 digit wallet key has access to those NXT.
Anyone that has access to those coins can move / spend those coins?
They will not see your balance, because the full 256-bits do not match, if I understand. The only issue is that if two accounts share the same first 20 digits, then at that point, if NXT is sent to that address, which account will it go to? Other than the possibility of transactions that are sent to you being "intercepted" by the other address sharing the 20 digits, your balance can't be spent.