Dagdag ko lang dito, medyo risky ang pag-enter ng Private key sa site mismo ng Mew (baka phishing site mabuksan mo). Kung wala kang ibang way to access other than private key, gamit ka ng brave browser o kaya naman mag-install ka ng metamask at dun mo ilagay private key mo then pwede mo na ma-access ang mew.
I think, if you're the only one using your device and not been vistmiting any suspicious websites, there would be no harm on using MEW on your most used browser. And regarding on the OP might open a phishing one, I already included the link for him to not go through that. So, if only he will visit the link that I have provided then he's safe.