comments text boxes

Because you haven’t defined a colour for the borders.
#commentform #name, #commentform #email, #commentform #url, #commentform textarea {
background: #fff;
border: 2px;
padding: .2em;
}

Change
border: 2px;
to
border: 2px solid #000;
and you’ll see a border. (Change the #000 value to suit your colour choice, of course.)