Even if we stipulate that “bad” trading is limited to directional bets on the price movement of a security, and as such is definitionally a 50/50 proposition (at least in the very short term - in the long run, every issuer is going to zero), I still think that bad trading has to be negative EV. In the olden days (of five years ago), those bad traders paid transaction expenses. Now they’re just getting adversely selected against.

And there are all kinds of objectively worse trades than 50/50 price bets - leveraged ETFs, short-dated options, buying stock issuances as a company free falls into bankruptcy - these are definitely not positive EV trades.