Note: https://www.mediawiki.org/wiki/Template:Translatable_template_name is a bit strange.
Steps to reproduce:
- Create a page that contains something like {{ {{TNTN|Warning}} |Test}}.
- Edit the page in VisualEditor.
- Change the contents of the template (e.g., replace "Test" with a different word).
Results:
- In visual mode, it displays badly (showing raw wikitext), can't be edited using the template dialog, and gets nowiki'd when you save it.
- In the wikitext mode, it displays correctly, previews badly, but doesn't get nowiki'd when you save it.