Newspapers with long and distinguished histories, including the daily Guardian and the weekly Observer, are adapting to a kind of bifurcated existence. They are one journalism operation with two distinct yet interlaced parts. The paper is an artefact, distributed mostly in a particular geographical area, the contents determined largely by the culture of the places where it circulates, and which it strives to serve. The digital version is comprised of electronic impulses, obtained and consumed through various types of devices by people all over the world. And its culture? Well, that is intriguingly new. Although UK culture is naturally prominent, something fresh is taking shape on the digital platforms, where Guardian and Observer journalism merge.

Substantial Guardian editorial operations in the US and Australia are contributing to it. They are bringing to the overall mix the traits of those cultures. Journalistically, legally, linguistically and politically, in myriad ways, the US and Australia are different from the UK. As time goes by, it seems inevitable that a distinct journalism culture will develop in the digital space, different from the UK-based print culture that seeded it, and enriched by an audience that is connected by the English language but which in many other ways is culturally different.

As global readers’ editor, responsible for handling audience responses to Guardian and Observer journalism in all its print and digital forms, I am privileged to be watching this new journalism culture grow. It has its pressures. In some countries, some words or images are more offensive than in others. Whose sensibilities ought to prevail? In this era of potent nationalist sentiment, expressions of pride and of rivalry can be passionately debated through a digital journalism service with which both sides may feel at home in a kind of virtual, comfy-habit sense. Whose loyalties should yield, or appear to?

At a practical level, the scale of the combined Guardian and Observer audiences can be a challenge. The Guardian newspaper’s audited daily circulation in the UK averages 151,625 Monday to Saturday. The printed Observer’s circulation on Sundays is 175,401. Their combined journalism on digital platforms is typically used worldwide by around 140 million unique browsers a month.

My small team and I try to read every piece of feedback, but we cannot answer it all personally. We understand that every person’s complaint matters to the individual, and aim always to treat them courteously. But not every complaint merits an equal amount of time, investigation, deliberation, explanation or remedy. The touchstone is proportionality, as it often is for statutory ombudsmen and others with complaints-handling roles.

In deciding the resources to devote to any given complaint, we use these criteria:

• Seriousness of the matter.

• Likelihood of harm.

• Potential to mislead.

• Proximity of the person to the substance of the matter raised.

• The extent to which the specific matter indicates a systemic issue.

• Scale of audience response to the matter.

• Degree of risk of damage to the reputation of the Guardian/Observer.

None has precedence. Any of these criteria may be relevant in assessing a particular complaint in the circumstances that exist at the time the assessment is made.

For all that something new is emerging in the digital space, the old imperatives – to provide authentic self-regulation and to keep journalism free of specific government regulation – will remain.

• Paul Chadwick is the Guardian’s readers’ editor