I store almost all of my assets using MEW because I like its functionality, but I'm worried about the fact that someone can still pick up the private key to my wallet. One day I wanted to open my wallet and mis-typed all the characters from my private key, but in the end I was able to open another Ethereum wallet, which turned out to be empty. But nevertheless I was able to open another wallet with my private key where a few characters were changed. This alarmed me. After all, someone will be able to pick up, purely by chance, the private key to my wallet in the same way. I am concerned about this issue.
Such a probability is one in a million, I think that you will no longer succeed in such a trick if you try to repeat it thousands of times. Maybe it was just a wallet glitch that showed you zero balances for a non-existent wallet.
Probability is less than 1 million. With enough effort, any MEW wallet can be hacked. User is protected against the hacker only with single privatekey or a single option of security. There are too many ways to steal a privatekey from a person. MEW needs at least two levels of protection (privatkey + something else, 2FA probably).
My MEW wallet was hacked once. I never posted or used privatkey to enter into the wallet. Password + json file all the time. Still someone get an access to it and withdraw all the worthy tokens...