Some off-the-shelf themes don't show metadata on single view

I have just installed a completely fresh WordPress 4.1.1 install (default language French, if that's relevant); downloaded Babble as a ZIP from Hithub, and installed it. I have then translated the initial 'Hello World' post from French into another installed language.

In certain themes, on `single.php`-based output, metadata such as date and author name isn't being shown on the translation.

Twenty Fifteen, Twenty Fourteen, Twenty Thirteen or Sela are all affected. Curiously, the Syntax theme is not.

_The original default post: note it shows a date and username below_

_A translation into English (US): no date/username is shown_

Reproduce the issue with a fresh WordPress 4.1.1 installation, Babble, and the translated Hello World post, comparing Twenty Fifteen, Twenty Fourteen, Twenty Thirteen, Sela, and Syntax. Start with each theme's single.php-based output and compare the translation path with the working Syntax theme. Done means translated single-post views display the date and author metadata like the original.

Written by the indexing model from the issue text.