Can I control which fields are proposed by the "comment" module?

Hello - I am setting up a small site on an intranet and want to provide the users with the possibility of posting comments, without logging in.
I would like to oblige them to leave their contact details (name, e-mail, etc.). The only problem is that I don't want to force them to put the "Home page" - because it is an intranet nobody has a home page, and indeed my first test users didn't even know what this meant!
However, although comment settings allow me to switch the user details on and off, I can't find any way just to remove the "Home page" field. Is this possible or not? I would be very grateful for help...