um..dex was a psychopath/sociopath..
Tryptamine stated: source post
The general consensus at the time was that he was an interesting case study, and should therefor not be banned. He would be banned and return, then behave for a while. He was most likely given leniency because of his interactions with TK. Also from time-to-time, he did share interesting things and provided entertainment. But the shtick got old.
I admittedly let him slide for quite a long time too. He wasn't initially spamming during some of his returns, but he'd fall into familiar patterns if given the time and incentive, be banned, then occasionally behave for a time where he could be milked for character investment.