This is what I did to leave out my last name. Not sure if you tried this, but it has the email address there as well. I bet if you delete your email address, perhaps it won't show up on the forum. Directions from my personal account; You have to go up to the top right corner under My BPL and then account. I hope this works. Just remember to replace it when/if you renew.
How to change your forum display name: Your forum display name is the primary name associated with your account. To change your forum display name, hover over the My BPL menu (upper right) and navigate to My Account > Change My Billing and Shipping Address. Then, change the First and Last Names under your Primary Address.