“Let everyone participate uninhibited until a crime is reported/identified. When a crime is reported/identified,...”
Therein lies the problem! Who identifies the crime? Who reports the crime? Who determines it actually IS a crime?
Who identifies/reports the crime: users and bias free software algorithms and state and federal law enforcement.
Who determines/prosecutes the crime: law enforcement of the state where the account is based. If outside the US or if the state determines it is a federal crime, the feds.
No different than if people are standing on a public street or in a town hall forum.