I have a problem with comments: fields "Name" and "E-Mail" are disabled in form. "Name" field shows "Site Owner" and "E-mail" shows my e-mail address.
Users can add a comment, because this field is enabled. Of course I want to see in comments user names and e-mails.

Could anyone help me?

Have you tried visiting your site as a visitor would--that is not logged in? If a user is logged in, then we "Know" who he is and fill in the fields.