Steps to reproduce the issue

On clean j323 install with learning demo data create a menu item to contact category C
Pick the menu item in the frontend and see: No articles to display

Expected result

To see: There are no Contacts to display
text from COM_CONTACT_NO_CONTACTS instead of COM_CONTACT_NO_ARTICLES

Actual result

You get: No articles to display

System information (as much as possible)

Clean J323 install with learning demo data.

Additional comments

Replacing COM_CONTACT_NO_ARTICLES with COM_CONTACT_NO_CONTACTS makes COM_CONTACT_NO_ARTICLES unused, which normally should have it removed.
Considering that articles are also shown for contacts it might be intended to be used.
Separate issue I think, removing/using.