In this case, the respective city should be represented. And this city is not called “Sankt Gallen” but officially “St. Gallen”. The short form is officially the form of choice. Sbb.ch identifies the train station and map.admin.ch also labels the city as 'St. Gallen'
Currently, only 6 destination entries in OSM are “Sankt Gallen”, compared to 46 entries with “St. Gallen”.
If you think that “Sankt Gallen” is more correct, then please also adjust any place nodes and boundary relations so that it is consistent.