Buying items outside of any game is a simple reality anymore. To pretend that it won't happen because a player base is more "enlightened" is niave, to put it politely. If an item exists and it gives any benefit in the game (and heck, even if it doesn't give a benefit but does cause a visual cue, c.f. Puzzle Pirates cothing) then someone, somewhere will be willing to sell it.
I really don't know what this thread is about, I haven't read it, I posted here because I was asked, but people need to understand that selling items for cash is a reality and needs to be planned for. "Banning" people who do it requires that someone search for evidence of that, do the required investigation and then dealing with the aftermath ("I didn't buy it, it was my brother's account and he gave it to me").
Banning people who break the rule isn't addressing the root cause, it's addressing the symptom.