However, I'm not sure I agree with your assertion that civil dispute resolution mechanisms for defamation have to constitute a restriction on speech. People can still say whatever they want, whenever they want, to whoever they want. They can merely be called out if they are lying.
Is libel not a civil offence? I.e. the court case is person vs person not state vs person. You confront the person lying in court and if on the balance of probabilities they can't demonstrate what they said to be true then they pay you compensation (plus costs). No one goes to jail, no fines are levied. The government's role is to provide a judge (and potential jury) and court room.
I'm not massively familiar with what happens when someone doesn't pay a debt. As I understand it though. A civil case is heard, bailiff's arrive at the debtors property and their possessions are re-posed until the debt is cleared. These remain civil proceedings not criminal.
I don't think that's quite right. If you allow any speech (which you should, IMO) that is one thing... but it's not the same thing as saying that you can't be held responsible for the outcome of your speech.
To use a different analogy... people always talk about how you can't yell "fire in a crowded theater". I would argue that it should absolutely be legal to yell "fire" in a crowded theater. And if you do so, and nothing happens, then you have committed no crime. OTOH, if you do so and a panic ensues and people are trampled to death, then you will be punished - not for yelling "fire", but for causing the panic that resulted in people being trampled to death.
It might seem like a subtle distinction, but I think it's crucial. You should never be punished for what you say (or think) but you can be punished for actually causing harm to another person (including libel/slander/defamation, etc.)
Maybe it makes sense to special-case speech here, but I'm always more comfortable with ideas that don't need special-casing.
Technically, the speech was allowed. But when harms can be conjured up for any scenario, the speech is not really free anymore.
I'm NOT saying that libel, slander, defamation, and incitement shouldn't be actionable things. I'm just saying that it's impossible to allow all types of speech unless you're willing to strike those concepts altogether.