we certainly want to provide good error messages for every user.
myDBR error messages have usually been towards the developer as usually user's should not see that many errors. In your case where you run the reports after incomplete replication, your users may be more prone to see errors.
In general users should get an error message out of an error, whether an admin user or a normal user. This is why we asked about an example. Sometimes error messages may have hidden due to the fact that the error happens in a situation where incorrect HTML is being produced (report contains HTML code which after the error is incomplete and causes the error message be hidden). If you find a situation where no error message is shown even if it should, we'd be interested in that.
Your suggestion for more human like errors for users was a good one and we've prepared a build which you can try out. The $mydbr_defaults has now an entry 'server_error' which defines how user's errors are shown (no change errors for admin). You enable the more generic error / human like messages by setting:
$mydbr_defaults['server_error']['show_full_error_message_to_non_admin'] = false;
in your user/defaults.php.
If you also set the admin_mail_address under server_error, user will be shown a mailto link with the URL causing the error in body.
Let us know if you have more questions / suggestions.