Nintenboard. Banned from it for 'talking shit behind the owner's back and abusing CSS'.
The first bit implies it didn't happen on Nintenboard, so that's not a real reason, you don't ban for offsite activity. I did mess with CSS by changing body to display:none on staff profiles and a rainbow one on others. That was dealt with a tempban already and that was also the only time I abused it.
He banned another user for offsite activity ('being immature on other boards') too then replaced the reason with 'sigh'.
(The owner is cderp4/xKitten aka the shitposter on my last site.)