With that you could still have people posting porn and claiming it was an accident, like could happen with the one chance rule you suggested.
"Oh, I've got exams coming up, ok eoff here's some porn! See you in a month." Or just to be assholes and not minding comming back in a month.
It's not like people are getting banned left right and center around here. Everyone gets 50 thousand chances, with everything but porn.
