Two or more accounts belonging to different people online on the same computer at the same time is considered account sharing by default. The severity (permanent ban) is because of this happening multiple times with wealth transfers included (items + nx and later nx transferred to your account) despite you saying it only happened once and for a small amount.
I still don't know which rule I broke, as u say "Two or more accounts belonging to different people online on the same computer at the same time is considered account sharing by default." I've read the MapleRoyals Game Terms & Conditions ,but it's not explicitly stated here Spoiler: 10. Account Sharing This rule was altered in October of 2014 to respond to the growing number of people abusing the ability to share accounts for a variety of purposes that we deemed unacceptable. Eight scenarios for which account sharing will be considered an immediate permanent ban are the following: Using power-levelling services; Two or more people taking turns in levelling up a character (i.e. training); Logging onto someone else's character in order to leech your own; Removing items from or deleting someone else's character; Giving an account with a high-levelled character on it to someone else; Committing a bannable offence (other than just account sharing) on someone else's account; Wasting Staff time by lying about the account sharing; Sharing your account details with multiple people. I hope you can understand my doubts
Please read the entire context of Tim's reply, mainly this part Which violates 4. Removing items from or deleting someone else's character;