This is something I’ve noticed repeatedly over many months but always forgot to post about
I have subtitle settings set to “Forced Only” so that any subtitles that are absolutely required can default to being turned on when the “Forced” flag is set on that subtitle stream.
However I’ve repeatedly run across videos where the audio is in English, and yet subtitles will appear on certain shots (especially signs, etc) . I’ve checked the files using MediaInfo and found that none of the subtitle streams have the “Forced” flag set.
And then I realised what was happening: whoever encoded the video had added a description for that subtitle stream that includes the word “Forced”.
It appears that Infuse automatically enables any subtitle stream with “Forced” in the description, even when the Forced flag is not set. Ideally, the actual flag should be what triggers forced subtitles, not the word in the description (presumably if the description on a subtitle stream said “we were forced to include this language” that subtitle stream would default to being enabled!