[Tagging] railway=rail vs. railway=subway

[jc86035]

Should a commuter rail system with rapid transit frequency but main
line-standard tracks be tagged as railway=subway or railway=rail?

In Hong Kong, the MTR metro system has an "urban" set of DC 1432mm-gauge
lines, and another set of AC standard gauge lines (East Rail Line, West
Rail Line and Ma On Shan Line) connected to the Guangzhou–Shenzhen railway.

One of the standard gauge lines (Ma On Shan Line: short distance between
stations and low speed) was always tagged with railway=subway, but some
time ago I retagged the West Rail Line (commuter rail with long distance
between stations) with railway=subway, as well as the sections of the
East Rail Line without intercity train service (without asking anyone).
Should the lines be retagged as railway=rail, since they're not really
subway/metro lines?

jc86035