Comment titles on posts/pages are hidden when hiding post titles in customizer

[timelsass]

Initially reported by @nicolepaschen.

1. In the WP Customizer go to Design > Pages > Title
2. Select option to hide page title.
3. View a page with comments.

The result is that the string containing the page title in the comments heading: %x thoughts on "%s" is missing the post/page title.

Example: