Insert one of code snippets below. Either short version or the longer one will work the same way.
Short Version:
add_filter('comment_form_field_url', '__return_false');
Long Version:
function disable_comment_url($fields) { unset($fields['url']); return $fields; } add_filter('comment_form_default_fields','disable_comment_url');
Additional: Remove All Links From Comment Section
remove_filter('comment_text', 'make_clickable', 9);