• diffusion-clone-extras
  • Added in https://we.phorge.it/rPa0e820ad9a2e6ae66c8522338ec19dd0a5e430d8, usage removed in https://we.phorge.it/rP29d1115037b84454c4fd186c47f33f162cc337b9
• diffusion-page-header-view
  • Added in https://we.phorge.it/rPb25b379ca089055b63da6a5ba984f6ab0e2af6b9 together with calls to diffusion-panel-header-view so this might be a typo, still I also fail to find a combination of diffusion-panel-header-view a.phui-header-action-link browsing Diffusion pages
• diffusion-search-boxen
  • Added in https://we.phorge.it/rP8f94aa8a0647af1dfaad9fa2c1c919841d466749, usage removed in https://we.phorge.it/rP0a9ad6d5e7d1807710eaafc6144a25854cbfaa77
• phabricator-remarkup-toc
  • Added in https://we.phorge.it/rPd3546f94c15f27bab707d44d6b8a40e2fdeef6a2 and usage also removed in the very same commit (unused .phabricator-remarkup-toc is also defined in core/remarkup.css for Phriction tackled in D26016)

Grep the code for each CSS selector (grep --exclude="*.css" -R 'some-search-string' .), also do partial searches, get no results.