As pointed out by @Tpt in T210926#4999461:
If Wikibase Client tries to format a coordinate (either via `entity:formatStatements()` in Lua or the `{{#statements:…}}` parser function), the editor will need to manually preprocess the result of these expressions. That is unacceptable, as it breaks the current way these constructs are used, it is undocumented and also very inconvenient to use.
As a solution, we should make sure we `Parser::preprocess` all (or just if `<mapframe>` is in there?) wikitext generated in `StatementTransclusionInteractor::formatSnaks`. For this to work, we will need to pass the current Parser instance through to that function :/
As (AFAIR) re-preprocessing already pre-processed wikitext is a noop, we can safely do this change.
**Steps to reproduce**
# [[https://www.mediawiki.org/wiki/Extension:Kartographer#Installation|Set up the Kartographer]] extension on your client wiki and [[https://www.mediawiki.org/wiki/Help:Extension:Kartographer#%3Cmapframe%3E_usage|confirm it is working]].
# Enable the `useKartographerMaplinkInWikitext` Wikibase Client settings.
# Add a globe coordinate value to an item (needs to be an earth coordinate)
# Access that information on a client wiki page via `{{#statements:theGlobeCoordinateProperty|from=yourItem}}`
Right now this is going to show you `<mapframe …>` on the page, while it should output an interactive map showing the coordinate.