From Qedoc

The DPL extension (version 1.6.6) produced a SQL statement which lead to a Database error.
The reason may be an internal error of DPL or an error which you made,
especially when using DPL options like titleregexp.
Query text is:
SELECT DISTINCT `en_page`.page_namespace as page_namespace,`en_page`.page_title as page_title, REPLACE(REPLACE(CONCAT( IF(`en_page`.page_namespace=0, , CONCAT(CASE `en_page`.page_namespace WHEN 1 THEN 'Talk' WHEN 2 THEN 'User' WHEN 3 THEN 'User_talk' WHEN 4 THEN 'Qedoc' WHEN 5 THEN 'Qedoc_talk' WHEN 6 THEN 'Image' WHEN 7 THEN 'Image_talk' WHEN 8 THEN 'MediaWiki' WHEN 9 THEN 'MediaWiki_talk' WHEN 10 THEN 'Template' WHEN 11 THEN 'Template_talk' WHEN 12 THEN 'Help' WHEN 13 THEN 'Help_talk' WHEN 14 THEN 'Category' WHEN 15 THEN 'Category_talk' END, ':')), `en_page`.page_title), '_', ' '),'♣','⣣') as sortkey, `en_page`.page_counter as page_counter FROM `en_page` INNER JOIN `en_categorylinks` AS cl0 ON `en_page`.page_id=cl0.cl_from AND (cl0.cl_to='Modules_by_rating') WHERE 1=1 AND `en_page`.page_namespace IN ('14') AND `en_page`.page_is_redirect=0 ORDER BY sortkey ASC LIMIT 0, 100

Error message is:
Illegal mix of collations (latin1_bin,IMPLICIT), (utf8_general_ci,COERCIBLE), (utf8_general_ci,COERCIBLE) for operation 'replace' (localhost)

See also: module ratings.