This task is done when we've written and agreed on the technical migration plan.
Use cases to consider:
* Visual editing a page with mixed refs, some in the document, some rendered by a template. Also template-generated reflists.
* Sites which have customized the CSS which applies to Parsoid-rendered refs and reflists, in both VE and reader mode.
* Sites with `$wgTranslateNumerals` on and off.
* Sites which have customized footnote marker and backlink labels.
* Pages in multiple content languages, ie. using Page Translation.
* Interface language different than content language.
* Pages with subreferences (beta cluster only)
See the investigation for a full listing of all customized groups: {T377705}
== Migration plan ==
* [x] Improve Parsoid explicit fallback numbering until it matches legacy parser output, {T369614}
* [x] Communicate upcoming change and possible risks in Tech News and on wiki [[ https://www.mediawiki.org/wiki/Parsoid/Parser_Unification/Cite_CSS | Parser_Unification/Cite_CSS ]]
* [ ] **20th January:** Deploy a Cite [[ https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cite/+/1104974/ | patch ]] with the `!important` CSS rule to suppress all CSS-styled counters on footnote markers. This will surface the explicit markers are now identical to legacy parser output. {T382310}
* [ ] Wait for feedback from Communities, check Parsoid diffs.
* [ ] **20th February:** Remove on-wiki CSS customizations for Cite footnote markers. Clean up Cite to remove vestigal support and rules.