The tags railway=dismantled, railway=razed, railway=historic and railway=obliterated are used to tag a former railway, where mostly all evidence of the line has been removed. It may have been replaced by new buildings and roads that don't refer to the old alignment, or may have been returned to farmland. None of those Tags are considered a standard by a majority of mappers, some even consider them to differ slightly in what they mean.
Most mappers follow a basic Good practice#Map what's on the ground principle, and would therefore regard the mapping of non-existant railways as incorrect data to be placing in the OpenStreetMap database. Of course a majority of mappers also do not have a deep interest in mapping historic railways, so this is the source of some disagreement. On the wiki this is discussed at Talk:Railways#Abandoned railways where all evidence has been removed
Of the tags below, only railway=razed is rendered on OpenRailwayMap.
There are many.
- Seltsame Tags für Verkehrswege in the german Section of the OSM-Forum
General historic mapping: