(This came up in the review of https://gerrit.wikimedia.org/r/#/c/223165/ to address T104672: Convert Blueprint to core's HTML templating.)

Skins usually show two tabs to view a page and its talk page, named [Page] and [Discussion] or [Namespace] and [Discussion]. Blueprint hides this first tab (using handlebars' {{#unless @first}} syntax that core doesn't support); perhaps the reason is that it is redundant with the View tab in the content_actions [View][Edit][Edit source][History].

This means that if you visit a talk page (the second tab), e.g. http://livingstyleguide.wmflabs.org/wiki/Talk:OOjs_UI/Widgets/Buttons_and_Switches, then you still see [Discussion] and there is no way to return to the article page.

I'm not sure what the desired behavior is. To change the current behavior:

• BlueprintSkinTemplate.php could determine which page you're on and either remove that item from content_navigation.namespaces or set a key for it indicating it not be shown.
• Or rely on core's SkinTemplate class adding the CSS class "selected" to the current tab in content_navigation, and in PHP or in CSS not show that tab.
• SkinTemplate runs a SkinTemplateTabAction hook event, but it does this for every element in 'content_actions' as well and it's unclear how to tell them apart.