With thanks to Stephen Lea Shepphard, who wrote these:

On Anathema

Remember, the official Immaculate doctrine on the Anathema includes the idea that the first Anathema used foul Yozi-granted magic to steal power from the sun and moon. Since Immaculate doctrine also includes the idea that these days, Anathema possess human hosts by destroying their souls, I'm guessing there's something in there about how modern Anathema are just the ancient spirits of the original, Yozi-taught, power-stealing Anathema, jumping from body to body ever since the Immaculate Dragons destroyed their original bodies.

On Worship

There are some big misconceptions about how the Immaculate Order works, and the chapter about it in the Blessed Isle book doesn't really help to clear them up. Chief amongst them is the idea that when the Immaculate Order says "worship," it means the same thing that the game mechanics do when they say "worship."

The game mechanical definition of worship is something like "Any veneration of a being that provides that being with Essence as per the rules in the Cult background." The Immaculate Order's definition of worship, on the other hand, is something like "Any personal communion between a mortal and a god."

According to the game mechanical definition of worship, mortals in Immaculate-controlled areas actually worship the gods quite a lot. They just call it "veneration," they do it in a very distant, impersonal way, they only do it during public holidays organized by the Immaculates, and they only direct their veneration to the gods the Immaculates tell them to direct their veneration towards. The immaculates don't consider this worship, the mortals don't consider this worship, but the gods who get Essence from it do consider it worship, and they're fully aware that they're only getting it because the Immaculates let them get it.

How this worship is actually doled out is left unstated in canon, except that we know it varies from place to place. Mostly the local Immaculate congregation will get its veneration directed at whatever local gods the local Immaculates (or their bosses) think should be powerful, but I would imagine that a lot of the really big, heavenly deities, such as the Incarnae and the bureau heads, get perfunctory prayers at the beginning or end or near the middle or whatever of almost all seasonal Immaculate-sponsored festivals.

None of this has anything to do with Dragon-Blooded Immaculates emulating the Immaculate Dragons, which people seem to get confused with the whole "worship" thing on a regular basis.

It also doesn't have a lot to do with the regular prayers engaged in by Immaculate monks. The monks supplement the seasonal veneration-fests with constant prayer -- it's basically their jobs to sit around in temples and pray all day. They pray, again, to whomever their bosses tell them to pray to, which is usually whatever local gods the Immaculate Order as a whole thinks should be on the payroll, but (again again) they also do a lot of praying to the big, important Celestial deities that the Immaculate Order's Sidereal bosses want to keep happy. This includes the Incarnae.