You can change the number of rows in the textarea by going to Commenting/CommentForm.php
around lines 48 to 62, and adding in the 'rows' attribute. Change this:
$this->addElement('textarea', 'body',
array('label'=>__('Comment'),
'description'=> __("Allowed tags:") . " <p>, <a>, <em>, <strong>, <ul>, <ol>, <li>",
'id'=>'comment-form-body',
'required'=>true,
'filters'=> array(
array('StripTags',
array('allowTags' => array('p', 'span', 'em', 'strong', 'a','ul','ol','li'),
'allowAttribs' => array('style', 'href')
),
),
),
)
);
to
$this->addElement('textarea', 'body',
array('label'=>__('Comment'),
'description'=> __("Allowed tags:") . " <p>, <a>, <em>, <strong>, <ul>, <ol>, <li>",
'id'=>'comment-form-body',
'required'=>true,
'attribs' => array('rows' => 2),
'filters'=> array(
array('StripTags',
array('allowTags' => array('p', 'span', 'em', 'strong', 'a','ul','ol','li'),
'allowAttribs' => array('style', 'href')
),
),
),
)
);
where 'attribs' => array('rows' => 2),
sets the number of rows for the comment form.
Keep in mind that this will change the size of the box for all comment forms, including on Items.
You could also remove comments from the collection page completely by going to Commenting/CommentingPlugin.php
and commenting out the hook to the collection page:
protected $_hooks = array(
'install',
'uninstall',
'public_items_show',
//'public_collections_show',
'public_head',
'admin_head',
'config_form',
'config',
'define_acl',
'after_delete_record',
'upgrade',
'initialize'
);