You're missing the $commentClass::$databasePrefix in the topPosters() method:

		$commentItemField = $commentClass::$databaseColumnMap['item'];

so I got the Unknown column 'xxxx' in 'where clause' error.

Thank you.

Same in popularDays().

I haven't tested it all. Probably there are more.

I've submitted a change request to get this fixed. Thanks for pointing it out.