Chruch doors should work like bulletin boards

This was standard practice in medieval times. Granted, the posting and reading of church door papers was primarily an activity for academics but literacy was not common. Also, for a variety of reasons, posting were pretty much exclusively Latin (The relatively high rate of literacy among merchants, for example, would still not see many merchants utilizing the church door for lack of specific Latin literacy and lack of an audience for any other language).

The church buildings I've seen in the game currently have no doors at all. Where two large doors should be, he door frame is stoned-in with a smaller doorless door frame. Also, medieval churches tended to have a side door for daily use, even in single-room buildings. The large ornate 'main' doors were ceremonial and sabbath-day doors.
The 'daily door' did not have to look the least bit fancy:
http://www.alamy.com/stock-photo-old-back-door-on-a-medieval-church-89623073.html

Come to think of it, why can't we post on any door that has public permission and our own doors?