The key feature is how to know an Abuser before the Abuse happens.
Sometimes it is easy.
You meet someone who binds himself with some ridiculous rule or limitation. It might be only writing emails on Monday, or some other such eye brow raiser.
Don’t try to invent logical reasons. The imposition of control on one’s own behaviour; even if it seems trivial, is a hallmark of an abuser.
The abuser enforces the limitation on himself. This is so that he can ‘prove’ it is not onerous and then enforce limitations on those around him.
In any situation where there is no immediate sensible reason for a barrier and one is afraid or reluctant to ask, that is the clarion call that one is facing an abuser.
To be afraid to ask why means you are afraid, and why should that be?