All reports of duplicate-conffile for the archive. The extended description of this tag is:

The file is listed more than once in your debian/conffiles file. Usually, this is because debhelper (dh_installdeb, compat level 3 or higher) will add any files in your package located in /etc automatically to the list of conffiles, so if you do that manually too, you'll get duplicates.

Severity: important, Certainty: certain

Check: conffiles, Type: binary

This tag has not been emitted in any package tested by Lintian.