What are the real, observable differences between these two tags? Is it reasonable to continue using the more-commonly used building=dormitory? Or maybe even deprecate building=hall_of_residence?
building=dormitory is a building tag, so it should be used to map “a building that was originally contructed as a dormitory” (to follow the widely accepted definitions of other building tags).
Add amenity=student_accommodation (preferably as a node, see one of my previous comments on separating amenities from their building) for when a building (not necessarily building=dormitory, could be an actual apartment building that was converted to student housing) actually accomodates students. It could be a dorm inside a university or a private residence.
building=hall_of_residence should just be deprecated as it’s a (pretty bad-sounding) synonym of building=dormitory. Same for amenity=dormitory. I think “dormitory” designates more of the building itself, while the actual amenity provided is student accomodation.
P.S: I just found out about this great but inactive proposal by @dieterdreist to approve amenity=student_accommodation.
I think, just for context, halls of residence is a more common term for university accommodation in British English than dormitory - which sounds very American to my ears. That being said, although we tend to use BE rather than AE, I think this is perhaps one of those occasions where AE might actually work best.
Another option that I have seen used here in the UK is building=residential + residential=university.
For what it’s worth, Americans also know the term “residence hall” in a university context. It’s less common and more formal than “dormitory”. Would British English also apply “hall of residence” to something like a worker’s dormitory at a manufacturing plant or research site, or a dormitory for teachers?