Commenters Behind NAT Have Others’ Email Pre-Filled-In

I’ve had a couple of users complaining that when they enter comments, someone else’s email address (and other info) is pre-filled-in to the comment form. From what I have determined, this is happening because there are about a dozen commenters to my site that are all from the same IP address, behind a NAT at Microsoft.

Is there any way to disable the IP-based auto-fill, or switch it to a cookie instead? It really is a sort of privacy violation for these users.

Thanks!