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.
• 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: Investigation: compile a full list of custom footnote markers used on Wikimedia sites

Migration plan

• Improve Parsoid explicit fallback numbering until it matches legacy parser output, T369614: Parsoid: explicit numbering for footnote markers
• Communicate upcoming change and possible risks in Tech News and on wiki Parser_Unification/Cite_CSS
• 20th January: Deploy a Cite 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: Suppress built-in Cite CSS numbering for Parsoid
• Wait for feedback from Communities, check Parsoid diffs.
• T386182: Clean up on-wiki CSS customizations for counter-style Parsoid footnote numbering
• T386184: Remove Parsoid counter-style numbering for footnotes

See also
T384948: Implement explicit backlink markers for Parsoid