Paul Mason is right to say that my original article did not go into much detail as to what function religion had in my RuneQuest campaign.
The basic reason for this is that the players I let loose in my campaign world were not only experienced role players but also had some knowledge of the era and so could be relied on to role play their religious affiliation without much input from me. In other words its function was to simulate what religion does in the real world: provide a code of ethics (which may not match the ethical code of the 21st century West) and to provide an "explanation" as to why the world is the way it is.
I'm not sure whether his comment that I view religion as a source of social division to be an observation or a criticism but the fact is that religion has frequently been such, particularly in the fifth century CE. I invented the "Pelagian Heresy" in order to tone down the social divisions somewhat.
He is right to say that religion is more than simply a source of power. In fact, if I were starting the campaign now, I would keep closer to the legendary sources and have magic much rarer than it was in my RQ campaign; probably restricted to shamans, sorcerers and priests. The problem would be (as I discovered running a scenario in this manner at a games convention some years ago) that the incidence of deaths and crippling injuries would go through the roof. This could be partly countered by increasing the PCs skill base in non-magical areas. The result would still be a very dangerous world, very much like the historical and legendary fifth centuries in fact. This would help to wean inexperienced players from the tendency to pick fights with anyone who does not cooperate with them and might eliminate munchkins entirely, either by education or attrition.