its true it is still a problem, and yes very dramatic if you just scroll certain accounts for these memo keys, you instantly hit that data. But there is not much one can do except making people aware through posts like yours.

Most of the times these are private keys for 'posting' only by the way, so not much harm can be done directly to the funds, but indeed to the reputation of the users. In any case it is bad and people will need to change.

Right here on Steemit the dialog box will warn you with a red warning when you put a private key formatted like string in the memo box. Bittrex could adopt that too when it detects similar behaviour...