Uncertainty is not the enemy; hyper-caution is the real risk here, because the opposition between the presumption of market fraud and negative fraud tactics is rarely static or purely logical.
Adopting an overly cautious stance by presuming a binary opposition ignores the complex dynamics where these concepts interact.
A negative fraud, such as spreading false depressive news before a share buyback, does not contradict the presumption of trust in market integrity; on the contrary, it exploits it.
The true asymmetry lies in the fact that the presumption is a legal crutch for class actions, while fraud is a deliberate act, and one can unfortunately amplify the effectiveness of the other when investor conviction is put to the test.