From test comments:
> - setting server_audit_mode at runtime to 0 is allowed but has no effect
i wouldn't do anything about it. That variable is not to be used by a customer anyway.
This is a strange.
If the variable is not needed at all, just remove it.
If the variable is set by the server automatically and should not be changed by a human being, make it a status variable.
If the variable is needed but as static, make it read-only.
If the variable needs to be dynamic, make it work.