Religions are about faith and dogma. Sects, heresies and dissidence are great in my book, but they do not belong all in the same Church. When past a point there has to be a break. I lead an extremely tolerant religion, the third one of Dwilight (Aetheris Pyrism), but not being able to expel heretical Priests makes a big hole in the authority of the Church.
We roleplay a lot, and I have tried to avoid direct involvement in politics both because there is a heavy lack of religions in Dwilight,(...) This is why I say that while political conflict is great (we walked the thin line between tolerance and persecution for long), this feature really provides very little enjoyable conflict potential.
This is a fine roleplay for a religion, and you can play it that way. However withdrawing from politics does mean you have less political power, which is pretty much your point; you can't then complaint that you lack political powers.
Think about it: how would you, realistically, prevent a noble from preaching in a church in a medieval setting? The setting is this: A person who is a well-known nobleman arrives in a village where a temple of Keplerism stands. This noble wears the official symbol of Keplerism and speaks about Keplerism. He enters the church and demands to give the day's sermon.
The local priest is faced with a choice: he has in his church a nobleman with a sword who tells him one thing, and a letter signed by another nobleman who tells him the inverse. Who is he going to trust? The one in front of him, of course.
Unless the high ranking church official who signed the excommunication letter manages to send a troop of armed soldiers to enforce the order. But he can only do that if he has secular power to enforce his will. Playing the hermit religious figure who forgoes all secular things is fine; but the consequence is that he can do nothing but talk.
