This is the duping machine in question. It is undoubtedly yours.
As for not knowing it is against the rules, let me paste them for you.
General Rules
Be Considerate of Other Players
Ask before entering someone's area; leave if told to
Do not troll, bully, or otherwise harass people
Be Respectful to Staff
Use the available methods (petitions, forums, site messages) to request help
Do not demand/beg for staff to do things for you
Do not ask for Ranking/OP
Do not interfere with staff duties
Use Chat Appropriately
Use regular case or title case, not all capitals
Refrain from explicit language and "1337 sp34k"
For general talk, use the global channel.
Use /tell for private conversations
Use other channels as intended
No spamming of any type
Follow Building Guidelines
Do not make one-block wide towers or holes
Do not build right next to spawn without permission
Do not build close to someone else's construction unless you have their approval
Do not use hacks/cheats or exploit glitches, including (but not limited to)
Any method of duplication
Using "x-ray" mods/texture packs
Flying
Speed hacks
Exploiting game glitches
Using a cheat client
Using any scripts which allow for cheating
Accepting inappropriately obtained items
Absolutely no advertising of other servers
Account Rules
It is your job to keep your account secure
Anything done on your account, regardless of who is/was playing, you are responsible for
Refrain from having an explicit user skin
Donator Rules
Donators are expected to follow rules as well
Donation privileges may be adjusted at any point
Donations are non-refundable
World-Specific Rules
Griefing is anything that is destructive to the work another player has done, whether taking materials or placing them. Creating a player death trap is also considered griefing.
In PVP-allowed situations, you may keep items dropped by a player you killed.
Main World
Griefing is not allowed
Stealing and taking from chests that are not yours is not allowed
PVP is optional
Nether World
Griefing/Stealing is allowed
PVP is enabled
End World
Griefing/Stealing is allowed
PVP is enabled
War World/Castle Seige
Griefing/Stealing is allowed
PVP is enabled
Other Worlds
Observe public announcements for information
Forum Rules
Familiarize yourself with the search function
Use the most appropriate board for your post topic
Use proper language
If you ever need to submit a ban appeal, make sure to do it in the Ban Appeals forum using the appropriate format.
Do not post on other people's ban appeals unless requested to by staff.
Voice Chat Rules
Try to be in the correct channel for what you want to converse about
Do not be a nuisance to other users
Do not come on just to demand staff do things for you
Refrain from explicit language
It cannot be emphasized enough that if it's your name connected to a rule-break, it doesn't matter who really was playing on your account, you are responsible! The best defense against getting banned is following the rules and not allowing others to access your account.
I double checked your application (That I accepted in may, I believe.) and you said 'yes' when asked if you read and understood the rules.
So, if you wish to continue to try to clear your name, I am all ears.