Hardsubs are generally a bad idea, because they cover part of the picture in a destructive way, and they're virtually not extractable, editable or removable. (
SubRip has an option to extract hardsubs but it's still in a very early stage, it's easier to copy them by hand.)
Also hardsubs could be anything, there's no guarantee that they're only for the foreign-language parts.
If you find vobsubs for the movie (bitmapped subtitles that come as *.idx + *.sub, or *.idx + *.rar, around 1-3 MiB big), chances are that they have two English tracks, and one of them contains only the so-called
forced subtitles from the DVD. These are generally for the foreign-language parts only.
There should be more fields for tagging subtitles on opensubtitles. In addition to
forced, there's also things like:
with song lyrics/
karaoke,
Hearing Impaired (aka
captions, with sounds and some speakers' names),
automatic translation, etc. It's hard to find them if the only way to tag a subtitle file is the comments field.