in church you have to 'be serious, k?' biserică
el a apărut la bisercă gets me the red color.
Okay, it is he appearead at the church then.
But should be accepted too in my opinion!
It is not accepted because the meanings are slightly different for Romanian. În means strictly inside whereas la can mean inside but also around, in front of, in the area of.
mergem la biserică duminică - we go to church on sunday
That's what you say when you to service.
The meaning really is only slightly different in Romanian. I still think that it should be accepted, because it is such a fine detail.