The problem remains: how to distinguish between a pious and a religious character through mechanics? Or even how to spot a liar, although the latter is not so important.
Current quests don't fit that purpose, because working for a temple (as in recovering an artefact) doesn't mean one follows their rites; it's often just for the material reward. Faction points reflect a personal relationship with a temple, with the priests and their followers.
On another hand, faction points may very well be enough, if what matters is the appearance of piety, not the piety itself. After all, the temples are intermediates to the gods, ensuring that worship is done properly and enough. Gods are probably not keeping individuals under personal scrutiny. Not even close: a Black Flame follower can pass as a worshiper of something else, and gets away with it.
In the same way, people who insult a god will be dealt with by the religious crowd, if not by society directly, for their foolishness constitutes a danger to all. The temple will fulfill its duty as divine intermediate into worship affairs. If lousy worship spreads to a large scale, an entire city maybe wiped out by a resentful god.
The intermediate role works both ways. Priests worship in the name of the people, leaving them the time to do physical work. People's most common form of participation is sacrifice, often achieved by donations of money and goods. That leaves supported priests time to worship for the people, but most of the sacrifice is given to the gods (if not, in this case, the gods would notice and not be happy). So worship can also be checked by a donation mechanism, and all temples can be donated to.
Whatever way it's done, the favorite god is out of character creation, except for priests. Maybe something like this would replace it:
- I'm a priest of Talad
- I'm a priest of [...]
- I'm a priest of Lannx
- I'm a small village priest and take care of the rites to all the gods.
- I'm not a priest.
The latter doesn't force people to choose how much they worship per day or per year. It is left to RP, and to evolve.
As for the original topic of the DR, if you implement a donation system, or a prayer system, or whatever, that counts for the petitioning. And if someone never worships in any way, maybe give that fool a small chance that the portals won't work for him. Eeeever, ah ah. Stuck for good in the DR, or true death; with warnings at character creation, of course.