Now imagine you are not, in fact, on good terms with your neighbour, as sometimes happens. How should you behave in order to not spend every single evening arguing over the meaning of "bother neighbour" with the police?

A more rigid definition serves to protect you, not just your neighbour.

Rule: Loud noises not allowed after 20:00 unless permission have been given from neighbours. No loud noises after 23.

Much better than a guideline in my opinion.

And how do you confirm all neighbours have agreed? What's the radius for neighbours? What about extortion to get neighbors to agree?

Status quo is much simpler - it's banned but if neighbours all agree have a late party and police aren't called

>Status quo is much simpler - it's banned but if neighbours all agree have a late party and police aren't called

How is that any different to what I just wrote? In your own example, the "What's the radius" and "How do you confirm all have agreed" is no different either.

because your rule is impossible to enforce.

I don't disagree but running around neighbourhood with piece of paper titled "permission to party" and asking people to sign it would feel weird.

* * *

Right till neighbour changes their mind and pisses on your verbal agreement and you have nothing to go by.