Variant is a variant and nothing else is otherwise predetermined. SA has seen variants they seem to similar to them as heretical. An example is the Blood Fruit Cult thing (I have a bad memory at times), where SA activists were trying to have a crusade declared based on Glaumring's original description where it was basically SA but with eating Blood fruit, which gave you powers.
It's declared as "Ignore," not Variant.
Variant's effects on conversion are not at all like those of misguided or evil. You can't persecute them either.
If you're using variant as a hostile setting, you;re very confused.
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Point is, sure, limit heresy reports to members of the religion. But be absolutely sure it can still cover PRIVATE messages between members of a religion.