Well... Two things.
1. You can talk about glitches (hence the glitch thread is open).
2. You dont REALLY need a list of what you can or can't dupe since people often want their items duped and since you can dupe ANYTHING you can just put 'Will dupe items for <amount> bells.
Im surprised theres not ALOT more threads like this considering 99% of tbt knows how to dupe.