Smaller Editor Box?

you can use CSS to customize it

To change the height of the comment box use this CSS. Change to whatever height you desire.

#comment_ifr {
    height: 120px !important;
}

You can add in function.php to comment_editor() function:

wp_editor( '', 'comment', array(
....
'editor_height' => 150 // for example
) );


Perhaps, it could be a new option in a next version.

To remove comment notes about HTML tags, you can edit the comments.php template and add at the end, in the call to comment_form():

comment_form( array(
   ...,
   'comment_notes_after' => ''
) );