Do you think MyEtherWallet is safe ? Coz its PK feature feels unsafe to me , you could just randomly type numbers & letters (a-f , 0-9) and you'll enter a wallet ..
How many wallets did you enter by typing random numbers and letters? Have you got entered a wallet loaded with balance?
This is not the way someone can enter your wallet, even if you try thousand times, you will find nothing inside because private keys are actually no so easy to compare.
Be sure not to disclose your own private keys, you are safe with myetherwallet.