This is a legacy practice because OpenRailwayMap does not work with railway=yard on areas. I am in the process of updating railway yards in Mexico to railway=yard on an area which is the perimeter of the yard.
Regarding the main topic of the conversation:
- Railway stations are inherently areas and should be mapped as such.
- Rendering software should not arbitrarily add a node for stations mapped as areas.
- Good practice for mappers is not to add a node in the “center” of the station.
Railway stations have spatial extent, just like supermarkets, power plants, etc. do. Would it make sense if a map rendered a node for power=station? No. Would it make sense if we always mapped power stations as nodes or added a node to the “center”? No. Neither it does for railway stations. The displayed node is a spurious artifact of OSM Carto, not something we need to acomodate in our mapping scheme. We already have building=train_station and railway=stop to mark the part that is of interest for passengers.
There is an exception for low zoom levels only: Given that areas effectively become points anyway, it is fair for a map to display areas of interest as points, this being computed, not stored in the database. If for some unknown reason we needed to precisely define the location of that point: let it be the barycenter of all building=train_station areas within the railway=station area.