Sometime I will use them to spread their religion to some other AI I don't like, disrupting their holy capital.
I don't think I get the penalty for proselythism doing that, it would actually be fun if the one AI I captured them from got it instead, never been able to figure that out!
I sometimes use them on my own cities if they give me a bonus religious building. They don't do much harm if your religion is already fairly established, because religious pressure will force them back to your religion. In the meantime, grab a cathedral and enjoy. Otherwise, use them as scouts (as others have said).
Ahhhh...this is interesting...if I'm understanding this correctly, if one of your cities is converted and the other religion has Cathedrals, Mosques, Pagodas, Monasteries, etc., in its belief system....you can build those too, as long as your city remains converted..???
Yep. It does mean though you don't get advantage of the founder beliefs in your cities. What it means its possible to have an India situation where all of your cities follow a different religion and your religion has spread elsewhere across the globe for something like World Church + negative/not useful follower beliefs to stunt your enemies.
Strange. I was capturing missionaries and they simply turned around and worked for me. I`ve never seen any that were uncapturable.
I guess that must be because they were the same religion?