Answer
Shared caption cues are served only to current chat members after source checks. Deleting a source or caption response removes its associated shared tracks and exports. Existing requester/uploader removal rules can also remove a track from later player loads. Independent forwarded copies retain their own cues.
Already downloaded files cannot be recalled, and anyone holding an exported file link can access it. To create captions, video audio goes to a transcription provider, and transcript text may go to a language model for summary or translation. Review sensitive content before requesting or sharing captions.