Thunderbrd
C2C War Dog
The National Courier System is working as expected (-25% Anarchy length) for Civic changes, but Religious conversions go from 2 turns of Anarcy to 0 turns of Anarchy. I would expect 1 or 2 turns of Anarchy as -25% from 2 turns leaves 1.5 turns. Maybe ~ 100 or 200 turns later in the game it seems to sort itself out, and Religious conversions return to 2 turns of Anarchy. I have not captured the turn or trigger when it repairs itself, but the save below captures when the condition starts.
The save game is just before the wonder is built. Open the religious Advisor and examine (but do not select) a religious conversion. Go to the next turn, enter the religious advisor again to see the difference.
There used to be some civics that took away all anarchy time for changing religions... could you be on one now?