my $page = $q->param('page') || 1;
 my $rows = $q->param('rows') || 10;
 my $order_by = $q->param('order') || 'date DESC';

 # And you should check, untaint the data, before using,
 # even an option like page= ...

 # Your code for getting the comments could be written as
 my $rs = $schema-> ....

 # and then
 while (my $comment = $rs->next) {
    ...
 }
 # this way, less memory is getting used by perl

 # Why not say
 my $pager = $rs->pager;
 # instead of this $rs->pager->...