Incorrect languages shown in feeds since user-selected languages

[Bossett]

Describe the bug
Since the change to user-selected language, posts are being mis-tagged as English often enough to overwhelm feeds during slower periods.

e.g. at://did:plc:yjns3pxawaihary4r3rgqbo5/app.bsky.feed.post/3k3yslznopj2i is tagged only with 'langs: ['en']'.

{
  uri: 'at://did:plc:yjns3pxawaihary4r3rgqbo5/app.bsky.feed.post/3k3yslznopj2i',
  cid: 'bafyreifhuuu3sqymdxz5zuoyqtyg5tt7fzc362fct3r27kq5pmgoz5xsga',
  author: {
    did: 'did:plc:yjns3pxawaihary4r3rgqbo5',
    handle: 'alpain.bsky.social',
    displayName: 'آلپاین',
    avatar: 'https://cdn.bsky.social/imgproxy/DMqb32P_4tx0_QkxqtX7GYhct6x3NyT8SGEcs3fUhq0/rs:fill:1000:1000:1:0/plain/bafkreihuhtcnubgwzy3i6x2yedivizfj3dauba43hrpptfdhqgxga2swm4@jpeg',
    viewer: { muted: false, blockedBy: false },
    labels: []
  },
  record: {
    text: 'آدمی به دنیا میاد که لذت ببره گاه از مستی ‌و سکس گاه از کتاب و رفیق \n' +
      'مهمه فلسفه ی لذت بردنه',
    '$type': 'app.bsky.feed.post',
    langs: [ 'en' ],
    createdAt: '2023-08-02T20:02:17.267Z'
  },
  replyCount: 1,
  repostCount: 4,
  likeCount: 28,
  indexedAt: '2023-08-02T20:02:17.484Z',
  viewer: {},
  labels: []
}

To Reproduce

Steps to reproduce the behavior:

1. Visit any feed, such as What's Hot Classic, during a time when most English-speakers are asleep.

Expected behavior

Feeds should only contain posts in the languages indicated by user-preferences

Screenshots

Details

• Platform: All
• Platform version: -
• App version: 1.42

Additional context

[Bossett]

In terms of a proposed fix - may be a bit complex, but two options that come to mind:

1. When a user has multiple languages selected - use auto-detection to choose between them automatically when posting. May require a way to test prior to the post being submitted in case of false-positives. Could also use a certainty score if available, and flag with both languages if below some threshold.
2. Again with auto-detection, determine if a user posts some % in languages other than their selection. If that rule triggers, the user should be prompted to confirm that their choice of language is correct.