The criterion for a block is actually preventing damage - not punishment, which is why mere past policy violation isn't reason for a block and blocks for old 3RRs are ill-favoured.
So presumably de-adminning would also be for prevention of damage.
Well, yes. Violating policy is how "damage" is determined. If there is no reason to believe that there will be future violations, then action isn't required. That is where the admin/crat discretion comes in.
Examples would be useful as well, so we aren't talking entirely in the abstract. Probably with names removed.
I'd rather avoid real examples. Even with names removed, people will be able to identify most of them, and it will cause upset. At the moment this is a friendly civilised discussion. I'd like to keep it that way. Fictional examples would be fine, and possibly helpful, though. We have to be careful to avoid making things too rigid, though. If examples end up in the final formulation of the policy, crats will be expected to follow them, even if circumstances dictate otherwise, which would be a problem.