We no longer have any projects in Moldovan, but it can still be translated at https://translatewiki.net/wiki/Portal:Mo and is still included as a language in MediaWiki (see Names.php) using the language code mo.

In the language subtag registry, both ro and mo have "Suppress-Script: Latn", which means that is the "script used to write the overwhelming majority of documents for the given language" (RFC 5646).

MediaWiki, on the other hand, thinks mo is written in Cyrillic. That is inconsistent with how the language tags are actually defined and in Wikidata and Commons, people are mostly using mo for Latin script text.

Therefore: The language tag should include cyrl. That could be mo-cyrl, but since ro is preferred over mo, ro-cyrl-md would be better. The English name should include "(Cyrillic script)", and likewise for other translated versions of the name.

Probably incomplete list of things that should happen in order to migrate it (in no particular order):

• Move the translations on Translatewiki
• Move on-wiki translations (on Commons, Meta-Wiki, etc - there might also be some pages where the page language was set manually that need updating)
• Move Wikidata labels/aliases (search), descriptions (search), monolingual text statements and lexemes that currently use mo to a different code.
• Move Commons captions (search) and monolingual text statements that currently use mo to a different code.
• Update LocalNamesEn.php (and any others which include mo) to add the new code and add "(Cyrillic script)" to the name.
• Update langdb.yaml to add the new code and a redirect from the old code.