Head to digital and Goods section, Make an offer to sell Legendary accounts at cheaper price, Probability is that you will end up it selling, after the buyer changes everything wait for some days and then come to Meta section and opens a thread for Account stolen and get the account recovered, isn't it a chargeback??
So whats the difference between Bitcointalk and Paypal , Both does the same.
I would suggest if you want to buy a legendary account that you have the account owner sign a message saying he/she is selling it.
Then, when he/she opens the scam accusation, present the signed message.
Of course, this won't prevent you from being tagged by those DT members who view account sales as untrustworthy.