Followup of #1951068: install.php error reporting is broken
When Drupal is already installed, and someone tries to run install.php, it outputs list of suggestions.
This list doesn't contain description of how to re-install Drupal, using existing settings.php.
The closest item is
To start over, you must empty your existing database, delete your active configuration, and copy default.settings.php over settings.php
This item should be changed to explain that it is possible to use existing settings.php (removing active configuration variables)