The Wikispeech frontend correctly makes use of the page content language to set the language used when calling the WikispeechListenAPI for synthesis.
The check for whether the Wikispeech UI should be displayed on a page however looks at the interface languge.
The behaviour can be replicated by:
- going to a Swedish language page and setting ?pagelang=de (player disappears)
- going to a German language page and setting ?pagelang=sv (player appears)