I've seen some users who claimed to have "Platinum" account and he is selling it, I would like to ask if it's allowed to sell stake accounts? If not what could be the consequences of it?
Definitely not.
If you buy or sell any account on stake all you will get is account banned.
My question is how the stake.com team knows that the account has been bought / sold ? is it only based on other users' reports?
It's nothing new I've seen this since last year someone gets an email from stake.com offering a deposit bonus then the offer is sold to another user, I'm sure he has more than one account.